Why am I so bloated/putting on weight?

I have never had a problem with my weight but for the past week, I have had a painful and bloated stomach most of the time, and no appetite. I have been eating in spite of having no appetite and I seem to be putting on weight... my stomach looks huuuge (and the weight is going to other places like my legs too). Do I have a backlog of food in me waiting to digest or something? I am going to try not eating until I actually get hungry... but I just don't understand what is happening to my body :( help please...