Please help, strange symptoms

Please can someone help, I had my period on the 11th of November and it was medium flow for one day then light for 2 days I normally have heavy flow for minimum 5 days so found this strange (I took pregnancy tests at the time but neg) I have been having strange pains in my lower stomach/groin area for a few days naw as well as a tiny spot of blood (only a smear when wipeing) the other day, I had a blinding headache this morning that felt a bit like a hangover that I couldn't get rid of without getting out for some fresh air. I have never ever had any irregularities with my period, any advice would be really great!!