I'm getting cold feet and my wedding is only four months away?!!?

Well everything for our wedding is done and planned. We are having a beach wedding. And we really wanted it as romantic as possible but now his mom and sister are telling us that they were mad we only wanted close family there (EXP mom,dads, and sister) But now we changed it to what they wanted and im not happy with it but nothing i can do. And im getting scared about getting married and just completley stressed and thats what i didnt want at all. and not it happening!! We have been together for almost three years. Lived together for one and let me say I'm only 20. I know age has nothing to do with but AHHHHH!!