Possible pregnancy? If yes, then when?

Had protected sex with partner on 4apr. Period date 20apr. (Took ipill on 16mar after unprotected sex within 6hrs of intercourse. Had withdrawal bleeding from 22mar to 27mar.) Signs of pms from 17apr. Worried if she might be pregnant History of irregular periods. Has changed her eating habits recently and sleep schedule has changed. Under a little stress because delayed periods and cannot tell her partner that. Could those be the resulting factors of late peroids? Is it because of the ipill? I've told her not to worry cause i read they can be the reasons for her delayed periods. But i need to be sure that I'm right. She can't really visit a doctor for this. Should she take a pregnancy test at home? If yes, then when? *Added some more details and posting it again