Hi, welcome and all that jazz....
This site (and I'm sure others like it although I stick with this one) are a godsend at times. It's great to know there are other people out there who have the same sorts of worries, issues and problems and it's a good place to get advice.
However, just try to remember that we are all people with our own problems and BPD to get a handle on. With BPD it's easy to think "these people are my new best friends. They all love me, accept me and understand me". That's the black & white thinking that is so prevalent amongst us. But, at the same time we are trying to live our own lives and sometimes you might find someone responds in a less than polite way, or that your message doesn't get any replies (yet lots of people view it!)....it can be very easy to get disheartened and depressed but try to remember that we're only human as well. And try to not use us to replace people you can meet out there in the 'real' world. Just because we have BPD doesn't mean we all think and feel exactly the same as you - sometimes you're going to have more in common with Joe Smith in the local cafe than you are with isoko49 from Scotland who just happens to have the same stupid condition!
Saying that - on the whole we are a great bunch and do try to help out as much as we can. There are people here at all stages of diagnosis (or not even professionaly diagnosed) and recovery. I've had my dx 2 years and am about 6 months into a real period of remission/recovery. But I still have my moments, because that's life with BPD. But with 2 years of therapy under my belt, I can rationalise my thoughts, feelings and actions a lot more. I have learnt how to identify my emotions (sounds simple to some people but very difficult for me as it goes from OK to overwhelmingly awful in seconds). And I am very aware of triggers and how to either avoid them (not suitable for everything - otherwise I would never go out my house) or how to handle them more appropriately so they aren't as massive or self-damaging as before.
Be completely honest with your therapist - they will become the person who knows you better than you know yourself. I won't say they will be your best friend because it is a professional relationship, but it's pretty damn close at times! Take whatever help/therapy you are offered, but be prepared for things to take a while to sink in. With BPD, it's taken years to get us to where we are, so it's obviously going to take some years to get us "well" and able to function reasonably well in the real world where other people don't get suicidal when their favourite TV show is cancelled. After 2 years of DBT (but not the official Linehan version - that just sounds mean to me) I have a toolbox of skills to call upon in any situation. Some of the skills I never use but others I use every day. It took 1 year to get my head around the concept of things being able to change, then another year to start practising the skills day-to-day and realise that changes were happening. Sometimes it feels like nothing much has changed, I still feel lonely, I still can't stop eating chocolate and I still cry at the drop of a hat.....but there are some things I have had to accept are not going to change because that's the way I was born. But I work on the things I can change and my life is more fulfilling and bearable. Yesterday I was totally miserable and depressed because my ex told me I wouldn't see the girls today (supposed to but he took them to see his sister instead), I know he's telling his family about his new partner but hasn't had the balls to tell me himelf yet, plus my car is broken and I need it next week to go on a first date with a guy! Plus it was raining cats and dogs, the house was needing cleaned, I have no money etc etc....but instead of wallowing in it (which is what I wanted to do) I went online and chatted for 2 hours on Facebook with said first date, texted my step-mum to let her know I was down, and next thing I know I'm smiling and having fun and my step-mum & dad are buying me a car. I then went on to clean the house and feel one heck of a lot better about things.....but I wouldn't have been able to do any of that a year ago. I would have been reaching straight for the razors or a lighter and self-harming. Even 6 months ago. It's small steps but you will get there.