hello... thanks for trusting the health care magic doctors for ur health related issues. first of all I want to tell you that . Relax.. nothing to worry. your girlfriend in safer side because u had already gave her unwanted 72 within right time, for that I m appreciating you. second thing is that u had sex during safe period in her menstrual cycle. so don t worry.. relax. pregnancy couldn t happen in ur situation. sometimes period will delay after sex due some hormonal effects in the body. good luck.. feel free to ask for further queries.