I am also amazed at how similar I am to you both HellsNotSoBad and aleezylove. For so long now I've done the whole running off to the toilets when I feel particularly ugly, hide in the cubicle and look in the mirror. A lot of the time I do my makeup in the cubicle because I can't stand people watching me do my makeup thinking "Ew why is she even bothering?" or thinking I'm vain. I check myself in the mirror ALL the time. In lessons at school I would open my bag and peer in trying to catch a glimpse of myself, to satisfy myself that I looked okay. Or I would look in the screen of my phone... basically any reflective surface. The weaker the reflection the better, so if I look in a shop window I often am quite happy with my appearance if my hair looks okay since you can't make out my facial features.
In the mornings I spend WAY to long on my makeup and hair. It's not even that I am putting much on, just looking at myself and putting little bits of foundation or eyeliner here and there to try and improve my features. Without eyeliner I basically look hideous for some reason, and the problem with eyeliner is it doesn't stay so I have to constantly reapply it through the day. No morning makeup application is the same. I apply the same stuff but somehow it looks different everytime, or my eyes look hideous. If my eyes look nasty then I basically can't leave the house since I feel they are such an important part of how I look. I never really go out unless I have to... thats not saying I don't want to, I really do a lot of the time. I will get dressed, do my make-up... and just look in the mirror for an hour deciding if I should show this face to the world. Most of the time it ends in me deciding I look too hideous and so I don't go out.
Anyway at the moment I'm 18 and I've just started university, and moved into halls of residence, and the first month was supposed to be the best of my life, but I've ruined it. The very first day I came here was a bad day, I had had my haircut recently and convinced that it made me look even more hideous (whenever there is a change in my appearance it will take me a while to get used to it, mostly as I've already convinced myself it makes me look ugly) so I struggled to talk to people and try to make friends. But for the first few days I actually smiled and laughed and came across quite well to people, however I then had another haircut to try and "fix things" and that was a huge mistake because I had just got used to the previous haircut and this one made me feel 10x more ugly. I didn't go out much after that, despite all the fun parties that were occuring, and ruined any chances of friendship with some of the cool people I met. I have hung out with them a few more times but I've been so consumed with my appearance, fearing they are all thinking I'm ugly, so I've talked very little and come across as completely boring. I'm convinced they all now think I'm a freak because I never go out and just pop up at times and am really boring. Sometimes I've forced myself to go out because I really need to make friends, but it was a big mistake because I just stand around worrying about my appearance, hiding the "bad sides" of my face, trying to get into flattering light etc... I can't concentrate when talking to people and they think I'm moody/don't like them because I don't show any interest in them due to my preoccupation with my looks. For nearly 10 years I've hated smiling with my teeth, I hate how it deforms my face and makes me look hideous. For a while though I've got over this and its amazing how people respond when you freely smile and laugh, they actually like you. But my "smile phobia" has come back, unfortunately if you don't smile and laugh then people don't think you like them or think you are boring, so this is basically what everyone I meet here thinks of me.
I basically never go out during the day (other than for lectures) as I think I look worse in daylight, so nights are my only time really for socializing. Unfortunately the few nights when I am okay with my appearance (At least at the moment I leave the door) I have nowhere really to go because I've neglected to make any real solid friendships in the month I've been here because I never go out with them due to my BDD. I'm scared to go over to their parties, which are literally just a few minutes walk away from my room, because I don't want to walk into a crowded room and they'll all be thinking "Oh it's her, she just turns up when she wants to" or worse "Ew she looks even worse tonight". I'm just so scared, and fed up. I had promised myself that when I started University I would turn it all around, I would not worry about my looks, I would smile and make friends and go out to parties all the time. I can't do this, I can't go to clubs and parties when they're all about how you look. I can't talk to people because my BDD makes me seem so boring it's ridiculous. I can't be myself because I associate myself with this ugly person. I try to act like other people all the time, people who are pretty and fun, but it backfires because it means people have no idea who I am because I'm always changing myself. My BDD/ugliness makes me grumpy, and who wants to make friends with a moody grumpy person? I just want to be happy and fun (but I always prevent myself smiling and laughing as it makes me look uglier), I want to be content with myself and able to relax in social situations. I'm always on edge in social situations, unless I've had a lot to drink, or theres just one or two people who I already know.
If someone compliments me, it will either boost my mood a lot and make me automatically very happy and hyper, or if it's some drunk guy I will assume he thinks I'm some ugly slag who will be an easy pull, and get very depressed. An amazingly cute guy whom I really liked that I met here said I was really pretty and I automatically assumed since he was really drunk that he was just saying the complete opposite of what was true, or he says that to every girl. I've basically blown any chances with him since he must now think I'm socially awkward/weird/boring since everytime he talks to me I feel so ugly. When talking to him (and most other new people) I feel so concious of how I'm standing and if it makes me look awkward/nervous, my facial expression (if it makes me look ugly), the angle at which they are looking at me at, the lighting... there is so many factors I think about whenever I am talking to someone, it makes it impossible for me to relax and appear... normal.
Sorry that was such a long post, I just really needed to get it out. I'm sat here all dressed up for a party, but I just can't bring myself to go. I'm scared that I'm wasting my youth, after all I can only get uglier as I age surely? The best time is when I'm slightly tipsy, but I have a glow about me and I look in the mirror and I look a bit rough but I still feel pretty and happy and good about myself ... why can't I feel like this all the time?