Hello I would like to know if I'm pregnant,I had sex last week on my period on the forth day but my periods are irregular for the pass 5 months now and I always had a 28 day cycle,bt now I get a 26,30,27 day cycles the cycle ws day 26 when my boyfriend came in me on my period from behind we had sex,and 3 days later I've starting to have a burn sensation in my vagina when I urinate in the morning it just happens in the mornings could I be pregnant?