What Causes Irregular Periods, Spotting And Abdominal Pain?

I have irregular periods. So I normally don t get them for 3 to 4 months and they last about 1 week and a half. My last actual period was in Dec. Then I noticed that I had some light bleeding in Jan and it lasted about 1 day and a half. It was a dark brown color. So I thought I was spotting. I thought that maybe I should take a pregnancy test. I took the test and the line that goes through the middle stopped half way. So I was confused. Thenot I waited a month later to take two other testes and they both were negative. I during this time from eversince i took my first test I have been experiencing lower abdomenal crampings. They were mild cramps. So it didnt bother me. Also I noticed that my breast were really tender and they still are tender. Then the beginning of March I started having really bad lower abdominal pain and cramps. Almost like a sharp pain. I wasn t bleeding but I just kept feeling that pain. Then two days later I started bleeding. It was bright pink and then it started turning bright red. Now its just red. It s not normal for me. I usually have really dark red almost brown periods. So noticing this is really odd to me. Then after two days my bleeding was getting even lighter but it was still redish to pinkish. Now I m feeling like I have to constantly pee and so I have to use the bathroom but there is blood mixed with my urine. I don t think I have a uti because I very had it before but it doesn t hurt when I pee and it was only today that I felt this way. I don t know what is wrong with me. I just want to know the possibilities of things that I could have?