I'm sorry man - I won't pretend to know exactly how you feel but I can really relate to most of the things you're saying.

Whenever I am in public (which I try to avoid because it scares me) and I hear people laughing but didn't hear what they were joking about I always feel like they are laughing at me. I feel that way even if I'm in my house and I hear the neighbors laughing loudly on the porch next door...

I block myself off from the world mostly too and I find the "real world" scary and threatening. I post in the AvPD forum sometimes - I'm not sure if I have AvPD or a mix of other problems that make me reclusive, depressed and socially anxious but I think everybody there can relate to what you are saying and maybe you can post there if you feel like it. Most of the people there do not have a formal AvPD diagnosis, we can just all relate to the symptoms a lot and are reclusive and kind of terrified of life...

I have also broken off contact with everybody I used to know or be "friends" with. I came to feel like I didn't ever fit in properly and at some point I started to feel like they didn't respect me and I was just an outsider who was trying to fit in (and I think I was justified in thinking that). Like you I have always been a really mellow and "laid back" person but I am prone to anger sometimes lately, more as I have gotten older - I think to some degree it's because I have a very hard time expressing my emotions and I hold them back and it builds inside of me and when I'm feeling down I can lash out in anger at people over silly things.

I have also been slowly retreating into myself - recently I'm only reaching outside of myself when it's completely necessary. Although, I have posted things here and in other mental health forums where I was asking for help and support and was hurt that people didn't seem to respond so much or even seem to care that I was trying to reach out and express my pain that I never express to anyone in real life... although I don't have a ton of "friends" here or whatever I have come to be more open with my feelings and mental/emotional problems here than I have ever been to anyone in my "real life"... most of the time I don't feel like people here are really listening or value me or whatever but I like to vent my feelings and frustrations here and at least I know people are reading it and maybe relating to it a little bit even if they don't respond. That makes me feel a little better than what I used to do which was say nothing at all and hold it all in completely.

Anyways, I know I'm ranting pretty badly at this point, but I think I understand how you feel. I am really struggling myself and I don't pretend to have all the advice or the answers but if you ever want someone to talk to or vent to then please PM me. I have pretty much no real life friends and nobody who PMs me so it would be a nice change to have someone to talk to. Over at the AvPD forum we are often "avoidant" of making posts but you might find that the people there can relate to how you feel if you ever want to post there. Either way take care and hang in there man... life is a ****** when you can't fit in and I'm barely scraping by.