How can I terminate pregnancy ?

Hi I have come off the pill after been on it for 5 years been on several kinds. I have been off now for 3/4 months, my periods are funny i was due on on a monday didnt come on till the friday only lasted 3 days then this month due on on monday didnt come on for 2 weeks, thought i was pregnant as was having all symptons, sore boobs bach ache belly cramps which are also signs of period... Confused im not in a rush to get pregnant but iv come off the pill to fall pregnant? how come iv been having unprotected sex, no pill??.. is they a problem because people say if your having periods it means your ovulating again??