Effect of drugs on menstrual flow. Do?

I'm a 25 year female. I experience regular periods with normal menstrual flow but with some uncomfortable cramps on the first day of my period. I was advised to take paracetamol to ease the pain. But when I take paracetamol, my pain is gone for few hours but I also noticed that my normal menstrual flow is very much reduced. So I stopped relying on any medicines for my cramps. But recently I was diagnosed with paronychial infection and was prescribed some doses of drugs that included aceclofenac, paracetamol and serrtiopeptidase together as a combination drug. Apart from this I was prescribed the antibiotic cefpodoxime protexil. The day of this diagnosis coincided with the first day of my period. The period flow was normal until I took the medicines. After an hour of taking the prescribed medicines I observed a drastic reduction in menstrual flow. But I cannot skip these medicines either. Is this normal? If not, what am I supposed to do?