I had 4 regular cycles after unwanted 72 on 13 march but in month of july I don't get my periods well I had 5 tests all was negative now I recently take a a test after 20 weeks of intercourse still it comes negative soo tell what was the problem of irregularities in periods. Plzz tell me as soon as possible and the last test I took was 5 days after my missed periods still chances of pregnancy.