Pregnancy problem. Is she pregnant?

Me and my girl had unprotected sex on 19th march after that she had regular periods on 30th march till 2nd of april on 3rd 4th and 6th she notice a drop. In month of april she did not get periods and still no periods. Its been like 2 months. She is waiting for her may month cycle which would be on 30th may.She did exercise from march to april 15th. Even her food habits were changed. We are worried that she is pregnant. She increased her weight from 49 to 52kgs.After regular periods, is there any chance of pregnancy, we are not involved in sex after march encounter. Me and my girl worried. What should be done at this time? Is she pregnant? We are worried totally. Moreover i did not drop sperm. Please help me with a helpfull reply.