I just started freshman year of college and I've been having a really tough time. A couple months ago I was super depressed and suicidal, and I've managed to improve a lot since then. I havent had any suicidal thoughts at all in a while. But I'm still having a lot of mental problems. It feels like I'm always super negative and pessimistic about everything. It's like I'm always worrying about some part of myself and I cant focus on anything positive. Something good will happen to me and I'll just blow it off and ignore it, but then something bad might happen and I'll be pissed off for the next hour. I havent made any new friends here. Everytime I meet someone I judt focus on whatever things I dont like about them and decide not to become friends with them. I always feel terrible about it afterwards, and its caused me to feel super lonely. I'm in the marching band, but that is the only activity I do outside of classes. I barely even talk to the people in my section, and tend to sit alone and not say anything. I'm pretty introverted so sometimes I want to be alone anyways, but even then I best myself up because I'll make myself feel like it's wrong not to socialize. 
This negativity goes beyond judt my social life though. I made it into a good school and I recently got an amazing girlfriend, but I just cant seem to focus about the positives. My mind always seems to be in overdrive and I overthink stuff a lot. It's like I cant accept the fact that I'm not perfect, and I constant feel like I have to improve in all of my negative qualities. Its causing me to be pissed off all the time and it's getting in the way of my studies as well. I know that I have a lot of anxiety, mostly social, so that might have something to do with it. My parents also raised me thinking I was perfect and if i ever mentioned any flaws, they would play it off as being normal, so I might judt have a hard time dealing with my negative traits. I just dont know how to fix this. I'm negative all the time and nothing positive ever seems to hold any value. Does anyone have any advice?