Could I be pregnant? Input please!?

I'm a 19 year old female and I've had irregular periods since I started at age 11. Because of this I would not be able to tell you the last time I had my period. Thus began my pregnancy test taking. I started taking the clearblue test's last week starting on 5-10-11, it was negative. I took a test again on 5-13-11 and it was negative. Then I took a third test on 5-15-11 and It was negative but it was not a clearblue test but a 99c store test instead. I kept feeling dizzy and having lower back pain. During all of this i found online that parsley tea was recommended to bring on a menstruation and I began making brews for about 4 days and wasn't aware that I was using Italian organic parsley. I stopped drinking and then I took another clearblue pregnancy test on 5-17-11 and it was negative. Then yesterday afternoon I went to gym and then to the market and bought actual parsley and came home and made a brew. I drank about 4 cups and began feeling a bit uneasy. Later around 8pm I began feeling a bit warm, I had a really watery mouth and sweating a bit. I then had to go to the bathroom and I took a pregnancy test again around 10:35pm and It had a line through it and very very very faintly looked like a positive result. I got worried and tested again at around 3:45 am only this time when I had woken up and I was bleeding a steady bright red color, but I continued to take the test and it looked like a negative result but later I could faintly see a line through it looking a possible but very faint positive again. The thing is I left the last 2 tests I had taken in the trunk of my car during the day and It was hot all day and they were still a bit warm when I used them. I woke up later around 9 and I was still bleeding bright red blood. So today I went to the market and purchased another set of tests because I read online that its possible to bleed while pregnant and it is still possible to get a positive if in fact you are pregnant. So I came home and tested again using a different brand named First Response. I tested it and the test came out negative. My question is even though I'm bleeding is it still possible that I could be pregnant? I still have lower back pain and I don't feel sick but I feel like I have a lump in my throat although I suspect that could simply be nerves.