I am 23 years old and have been on birth control for about a year and a half. I am usually quite regular, sometimes starting my period just a couple days late but never early. This month, I started my period two weeks early. It was normal flow with a lot of cramps, pain, weakness, nausea etc. After one week of that, I had one week of a very light period, mostly just spotting. Now, on week 3, I have started over again with a period with normal flow, cramping and the whole bit. I am unusually tired and have had days where I have been nauseous, have had frequent headaches, experienced some pain, and have had pretty bad pain during and after sex. I really want to know what my problem is.