You are still sooooo young, and you do not sound fat at all---I'm sure you're lovely, and believe me when I tell you that 10 years from now you'll look back at old pictures and think to yourself how beautiful you were! We are so much fairer to ourselves in retrospect.
Also, remember that any auntie who is obsessing over shallow silly things like weight, height, skin tone, etc.,** is not worthy of being your mother-in-law. ** I mean, is that really the type of woman you want to listen to for the next thirty years while she makes passive-aggressive comments about all the tall, thin, fair girls she looked at for your husband before you (or for your brother-in-law, cousins, etc.)? Be patient; God always provides us with opportunities at the right time, and eventually people of real substance will come meet you and be able to see and judge all of the things that really matter---like your character, your mind, etc.