I need opinions

For the past week I have felt very tired, I am so tired that I fall asleep during my college classes. I dont like coffee much anymore, my lower back hurts, my body feels weak, and I keep having cramps around my uterus. What is the cause for this? Few weeks ago I took many tests and all were faint positives but I had a negative blood test. When it was time for my period it was only 2 days and it hurt really bad. I took a test and a dark line appeared within the time frame. But the strangest thing happened, the line moved slowly and disappeared leaving a thick white line. I think it is just an evap but I never seen it like that before.