Pregnancy Symptom or Something More Serious

About 3 weeks ago I started taking prenatal vitamins, but my inner thighs and genitals started cramping so I stopped taking them for 5 days. I felt a little better, but found out yesterday I am 4 weeks pregnant....I took 4 pregnancy tests-all positive. I started taking the pills again cuz I thought maybe I was just experiencing pregnancy cramping. Well the cramping is back... do you feel this is something I need to worry about? I am going to call my doctor tomorrow to explain what’s happening.