So yesterday wasy birthday my mom bought me a cake and so did my mother in law what do I do with them so I won't look rude I haven't taken a bite of neither and honestly I don't want to I have a huge sweet tooth I'm scared I might start eating everything in my path ...
Umm... Invite some friends? Give a cake to someone else, like neighbours or I don't know...!?
That's a really difficult situation indeed.
I have a massive sweet tooth as well. If you can't trust yourself to eat a little bit at a time, I like Nikki's suggestion, eat a small slice then get rid of the rest of it. That way, if they ask you how you liked the cake you can answer honestly. I'm sure (I hope) they don't assume that you're going to eat the entire cake by yourself!
That's a tough situation, but maybe you can use it as an opportunity to explain how you're trying to eat more healthy and you want to make good choices, etc.