Agreeing with Kyrul here. Also, sadly we live in a society that automatically puts pressure onto those who aren't stick insects and it's terrible- but you have to say to yourself that well... why would you want to let a comparison get in the way of you living your life? And attractiveness is very much personal opinion.
I say stop with the comparing and focus on you. Focus on living your life and focus on the fun and good times. I don't believe anyone was "made ugly" because once you hit a certain age, you realize that beauty isn't in the way someone looks, but in their heart and their intentions and how they carry themselves. And there is a lot that molds you into the way you are today (even posture will make a difference in your appearance!) Yeah I know that sounds a bit tacky, but I've also been through self esteem issues (I also used to be overweight, have skin conditions, was mocked when I was younger, and I'm even now mocked because I'm only 4'10".. and that I REALLY can't change about myself.) but why should I let that affect the way I want to live? I think you need to change your outlook, but I understand your frustration of wanting to be sexy or beautiful. Try and tone the comparing down, and even throw some of the jealousy aside, and focus on you and what IS good about you (heck I can already say you are humble and present yourself through words very well, already, and I am sure there is more good about you too) and if there are things you dislike, then you should experiment with them! (Try a different style or things with your hair or do your nails, etc.) Find little things that make you feel pretty, and DON'T say "oh well ___ has better ___ than me so what's the point in putting in the effort?" YOU are the point. So yes, put in the effort to feel good about yourself. Knock down those mental boundaries.
Anyways, I recommend you might see if your college offers an on-site therapist to help you with social anxiety. If you're worried about your weight, then take steps to either be accepting of it, or change it.
As Kyrul says, it's mostly in the mind. And heck, I am sure your boyfriend and family think you are a beautiful girl, no doubt. And honestly, if someone else were in your position on how you feel.. what would you tell them?
It's difficult to try and build confidence but try and do so through YOURSELF and your accomplishments and feeling good about YOU rather than trying to build confidence through other peoples' positive comments, because you will end up holding those comments to more regard than they are actually worth.
Good luck and feel free to write in here again if you are still troubled.