I am 21years old... after four months once only I vomited... my physical growth also didn't change... is there any possibility to get pregnant after four months... I had means last four months... so how about the chances?

If you haven't had sex in the last four months, and have been having regular periods, it would be unlikely that you are pregnant. If for some reason you feel that you are, or just want to check, try a pregnancy test.