It could also be that you are depressed and in need of a medication change, and the depression colors your thoughts, so you THINK that you do not want your bf to touch you because you are fat, but in reality it is your depressive anhedonia that makes you not want him to touch you, and your mind finds a rationale for anhedonia - "I feel ugly and fat". As advised before, think of it rationally - if he wants to touch you, he finds you attractive, so you really need to see a psychiatrist and tell him what you have just told us.