Well I went to bed angry last night cause FI knew not to talk to me when I am like that. This morning I woke up to breakfast in bed and him saying he was sorry for the way things happened last night. He was sorry that he didn't let me know they were coming and that he did not check his sister for talking to me like that. He told me that he will make sure that will never happen again.
He also told me that his mom meant no harm she is just really excited for us. So as soon as he said that I instantly felt awful for yelling and putting them out. I called her, and apologized for my behavior. I just felt ganged up on and I did not like it. She started crying and told me that she loves me and she knew that she had crossed the line and she was sorry. She also let me know that her daughter will never make another comment about my weight. She asked if she could still be a part of the wedding and I said of course. I did let her know that it is mine and FI's day and ultimately we will have the final decision about anything regarding the wedding. She agreed and now things are right in the world again.
So from now on ladies I am gonna try my best to keep my calm and think before I react. Thanks for the support ladies. You have no idea how much you guys mean to me!!!