My Last Period Was On The 26 Of August. I

My last period was on the 26 of August. I have been feeling all the early pregnancy symptoms but all my pt test have been negative until 4days ago when I got a postive result. I started bleeding a day after d positive result. The ultra sound says there's imminent Cyesis. My doctor gave me a shot of Primolut depot and some drugs yet I am still bleeding 3days after, mild cramp, no pains,two thin tissues passed, it's just like a normal period. I want to know what is going on with me.