wow, I am just the same!
but only some of the time. sometimes I feel fine about myself and that's mostly when I am by myself and I am not surrounded by people I compare myself to or who criticize me.

I am in a very competitive environment and it really gets to me. as a child or during school I used to be the best at something I was doing. I wasn't pretty or popular but I was clever and among the best students in that school. but when I went to study there were lot's of people who used to be best at what they were doing at their schools.
so it's hard to get used to not being best anymore.
and on top of that they were all pretty and popular!
and on top of that being pretty and popular helped them to be even more successful.

that makes me feel awful at times.

but sometimes I talk to other people who do completely different things and I tell them about my life and I realize how great it sounds when I tell them what I have achieved.

I know that there is always someone in this world who is better at something. we do have to deal with it. but it doesn't mean they have better lifes though.
there is one person I really admire a lot and I am jealous of his career and his skills. but he is a heavy alcoholic, uses lots of drugs, and his wife left him. -so I don't want his life! no need to be jealous here. I just have to remember that sometimes.

and perfectionism I know well, too. the only way to get out of it is when you decide to say "it's fine" and then it is fine. you need to put a limit at some point. because otherwise it goes on and on… never ending, forever bothering you. no matter how great you already are!