Depression?!

I am after some advice. I believe i have some form of depression but not sure what type.
I have quite highs and lows, not manic but mildly so. I have days where i feel invincible and feel so happy and on a high i sometimes ger heart palpitations. But then i get lows, am on one now. Where i just feel, well, nothing. I dont want to talk anyone, i just cant be bothered to do anything. I want to cry, and may even do, for no reason. I feel exhausted and drained but i get 8 hrs sleep a night! My real lows only normally last a few hours, then i take a few hours to get back to normal. When normal i still feel exhausted quite often. I am currently loosing weight and eating healthy, although i sometimes 'binge' when i get cravings for fatty food. Its almost like a dark cloud that comes over me then slowly lifts.
When driving home tonight i find my mind imagining my car crashed and that i am in hospital and wondering what people would think. I dont actually get the urge to crash the car!
I lost my grandma in january and having worked in care previously i am really concerned about death. I worry constantly about friends and family dying and how i will end up before i die.
I get quite angry and snappy very easy. I have a short fuse and can get quite worked up over even little things. I then feel bad for these outbursts as they effect other people. I try to keep my moods to myself but when on a big low like tonight i cant hide it.
Does anyone have idea what type of depression this might be?! Or have any advice if someone has a similar problem.
Thank you.

We can't diagnose you but it looks like you're going through a very difficult time and it's obviously effected your emotional and physical health. Also when you said that you like to keep your moods to yourself, bottling things up won't help. It might be a good idea to see your doctor about these problems so they can advice you further on the next step or go to a counseling service depending on your country but I know in the UK we have plenty of services that don't require any referral from anyone else if you don't feel like going to the doctors. I don't have the exact same problem but I do suffer from depression and anxiety and have been put on antidepressants and have been referred to therapy so speaking to someone did a world of good for me. Take care.

Have you always felt these things, or were they brought on by your grandmother's death?