Well, it could be a number of things. I know that birth control can cause weight gain. As far as being lazy...maybe your having issues with your sugar levels? Pregnancy can also cause fatigue, which in turn can cause laziness lol.
As far as your pains go, I would highly suggest seeing your doctor. You could have what's called an ectopic pregnancy, which is a pregnancy in your fallopian tubes, and it can be fatal if untreated.