Can Mini Pills Cause Cramps?

I have been on the mini pill (norabe) for years. Since I've been on it I've had pretty normal periods and very very mild cramping. Last May I started getting nauseous about a week before my period. I wake up nauseous and eating seems to make it better but I can usually only take a few bites before another wave of sickness comes on. This has come and gone for months, some months I've experienced it while others I haven't. The past couple months I have been very irregular and only had one day of spotting with bright red blood when I wiped at the beginning of Feb. I have taken pregnancy tests before and they have come back negative. I haven't taken one yet this month. I have also been having burning like cramps the past week and right after the last two times I've had sex. What could be causing this nausea?