Can anyone help? im slightly worried what this could be? ?

Ok so basically I just didn't know what's happening to my body, I have put on so much weight the past month,maybe 2, but for instance 5days ago I fit fine in my pj bottoms and now ttheyre really tight across my bum which is strange how iv put on that much weight that quick? I also keep fancying cheesy chips or bigmacs, basically a few of my mates thought I could be pregnant however I am still currently taking my pill and have been drinking a lot as obv I didn't think anything of putting on the weight but also I keep bleeding even though I am on the pill? Any ideas? X