Help! I have missed my period. I am late for 3 weeks, I have pain sometimes at night like I'm going to start my period but I don't. I'm very tired all the time and hungry. Sometimes I have diarrhea. I feel sometimes like I have gained a lot of weight but it might just be from all of these problems. I haven't been dieting, working out hard, or been under stress. I thought I might be pregnant but I used two home tests they were negative. I am scared, I just want to know what problem I can have?