Talk to Gynecologist on Periods Stopped

I had pain in left side of my neck, back , the area under neck and arm... went to the physiotherapist and he suggeated therapy and a medicine capsules for pain relief... but the day i started taking i had my periods and as soon as i took the medicine the periods almost stopped.. to spotting m taking ds capsule for 3 days and the periods have almost stopped..y?? Any serious issue?? Wat should i do now???i am also suffering from toothache and the doctor has given me tablets flexin 500 mg and tablet prevent( tinidazole) 500mg... i have not started taking that yet qk mje dar tha os se periods na ruk jaayen plx help and guide