Pregnancy related. From last 21 days?

Hi, i had normal period in october 2016, but after that no normal period. In november i bled for 2 days which was dark brown blood not same as periods blood. I took a hpt bt it came out negative. Also consulted a gynaeo, did beta hcg, it also came out negative. In december i didnt get my period. Then i chnged my gynaeo, went for ultrasound but no sign of pregnancy. She told me there was infection and prescribed me medicines for periods. Then i got very light spotting for 2 days and after 8-9 days i.e in jan 2017, i had some bleeding which lasted for 1 day only. Then my gynaeo started meprate for 21 days for a normal period. I wanted to know if there is any chance of me still pregnant bcz in this duration i puton some weight, having constipation, bloating, gas, tiredness, fatigue. I dont know that if these are side effects of taking meprate. And if there is a chance that i m still pregnant then what about me taking medicines for normal regular period from last 21 days? Pls,help me. Thnx