Whats wrong with me? Any ideas?

For the past 3 months I have been feeling weird. My periods have been late, in May it was 4 days late and same with June but this month its 7 days late now. I was supposed to get it Friday last week. My periods are usually normal. Oh yeah and they have only been lasting 3 days normally its 5 days. I'm always hungry, I used to be able to eat 1 1/2 meal a day and be fine. Now after I eat I'm either never full or a few mins later I'm hungry again. I have also been bloated all the time and having a lot of pain in my abdomen, not sharp pain but almost a crampy pain but not quite and it fells a little different. That happens about a week to every other day. One more thing is that I'm WAY more tired than I ever have been, I used to walk for about 2-3 hours a day in the evening plus whatever I do during the day. Now I can't walk a block with out getting tired or feet hurting. This is really weird for me. Any ideas on whats wrong with me?