My period has always been irregular the longest I went w/o my period is 2 months and that happen only once. My regular period pattern is I would come on for 2 months then skip a month and so on. Me and my boyfriend had sex and he did nut in me and every time we had sex after that day he still did. My period stop and is still not on. I went to the doctor and gave a blood test. The test came back I was not pregnant but my period still isn't on and this makes 4 months now 5 months will be next week. Why is has my period completely stopped if I'm not pregnant?