but then this morning my mum asks if i am preg because i look like i am.
WTF!!!! I may be out of line here but WTF!!!!! I would just snap back and say: "lucky I'm not you that carry twins in my A$$" No matter how thin/big she is!!! Really that is not a nice thing to say to your daughter.

Hun, your not stupid. And speaking to a counselor is a great idea. And taking to a counselor about weight issues are NOT silly!! In fact I think it would benifit you greatly.

Hun, what is your BMI??

Hope you get someone that can help you IRL