What could be the female issue?

I’ve had nausea around the same time every day for almost three weeks now. The home pregnancy test was negative. My periods have been way early (last time it came within 20 days of the previous) and way late (this time it came on the 2nd of June after ending on the 26th of April). I haven’t made any drastic changes in my lifestyle.

Any experience with this?
What should I be doing?