Pregnant or not?

[slspringall]

I am trying for a baby. I came off the pill in November after 36 days finally had a period on the 15th December. I then wasn’t sure when I was due on again but took it as another 36days. In January on day 25 and 26 I had brown spot bleeding. Then on day 32 was light bleeding, day 33 and 34 heavy and light again day 35. On day 35 I had a severe headache like my head was going to explode and although not as severe it’s lasted 5 days. Yesterday I was sick in the evening and felt nauseous all day. I did a pregnancy test and it was negative. Today I found it as I’d forgotten to throw it away and there was a positive line! I did another test and it’s negative! I’m very confused? What is wrong?