hey, u definitely need to build up ur self-confidence. I'm glad you're asking for help, because it means that you've realized ur jealousy is a problem. there are various ways to deal w low self-esteem, imo.
♥ for starters, u can try practicing this exercise: every day, get ur butt in front of a mirror and look at urself. when we look at our reflection, we tend to fix our eyes on the stuff we like the least, and not on the overall picture. for starters, u might be staring horrified at ur big nose, ignoring the plump lips, or thinking about the strawy hair, but ignoring the pretty earlobes. every single day, say something about you that u like. it doesn't even have to be physical, it can also be personality-wise or with regards to ur abilities: u might suck at cooking, but be an excellent violin player. try to do this every single day. u'll get there.
♥ try a change of look! try out new clothes, consider a change of hairstyle or just make-up. whatever makes u feel confident and sexy, wear it. also, try using sexy underwear under ur everyday clothes- it can increase ur confidence significantly. at least, it works for me
♥ EXERCISE! I can't stress this one enough. whatever sport u like, practice it. it'll make u feel a lot more better with urself and ur body. trust me. also, it can get rid of some insecurities. if u feel bad about ur butt, do butt exercises. if u don't like ur unshapely thighs, target that zone.
♥ try to dedicate more time to stuff u like to do, in other words, build urself up as a person, innerly-wise. when u do stuff u like to do and become good at it or at least make progress in it, u feel better w urself. you'll also have more topics of conversation
♥ write them down! u know ur jealousy comes from being insecure. well, write down ur insecurities. however long the list is. and then, write besides the insecurity, write in another color what u think a friend/family member would tell u if they knew about it. the thing is, we tend to be overly-critical with ourselves, and a lot kinder to everyone else. that doesn't lead us anywhere. instead, treat urself as if u were ur own best friend, and give urself words of encouragement and cheering every time u look at a mirror, never the opposite.
♥ FAKE IT TILL U MAKE IT! honestly. this phrase is underrated. u might not feel confident, but u CAN act as if u were. get urself out there. hang out w friends, do stuff u like to do, get into ur head that u are in no way inferior to any other lady out there, but equal. to me the game changer was feeling good about myself and seeing how some people tried to make me feel insecure again. I realized that the problem wasn't mine, but theirs. get that into ur head, too. u are beautiful, u are smart, u are whatever the hell u want to be. if u feel beautiful, you'll be beautiful.
as a brief conclusion, can I just say confidence makes up for looks ANY DAY. I can't count the number of times I've repeated this on here, but it's completely true. ur attitude is what changes and ups the game. trust me on this. also, it's good u are communicating w ur boyfriend about ur jealousy, it's a good sign. however, realize jealousy is a very toxic and damaging feeling in a relationship, and that u need to do something about it before the relationship can't handle it any more. a relationship which lacks trust isn't worth fighting for, imo. if it gets really bad, u can always speak to a counsellor
good luck! <3