I am 18 years old. All of April I missed my period. I got a very faint positive pregnancy test, after that all test were negative. On May my period was late two days. I began to have brown spotting. Pregnancy test was negative. I spotted for about 3 Weeks light pink and brown. About 4 days after started a normal period. All my lower stomach hurts and I have nausea every night sometimes all day. My bones ache, I don't even feel like getting out of bed all day. My head feels like its going to explode and my stomach growls all night, but I've never ate late. Im trying not to eat much, but I'm still gaining weight. What can it be?