My girlfriend and I had unprotected sex while she was ovulating but afterward her period came on time and was normal she then ovulated and is currently on another period which was also on time, although this period is much more painful (she feels cramps in her actual vagina)with less blood flow so is this normal or should I be buying diapers? Thanks every answer is appreciated.

Does not sound like she is pregnant, perhaps just a bad period this time,
Perhaps time to invest in condoms and birth control pills unless you are trying to have a child