I think you should go and talk to your doctor.
Find out what is behind this.
It could be a lot of things as people have said.
Your doctor will be able to do tests to see if it is to do with your metabolism, your thyroids etc. Or if its just to do with your diet.
It might also be an idea to keep a (completely honest) food diary for a couple of weeks so you can show your doctor exactly what you have eaten.
Goodluck with things!