Bleeding at 8 weeks ?

I am 8 weeks pregnant, I started spotting at 7 weeks (last Thursday). I went to the doctor Friday and they did a pelvic and ultrasound and everything was fine. They also measured my Hcg levels and they were fine. They had me come back on Sunday to monitor my levels. I stopped spotting. When I went back I found that my levels had went up but did not double. I started spotting again the middle of this week. I have another sonogram tomorrow, but I started to bleed heavier today like the end of my period. I have no cramping and no clots I ddidn't know what to think. Anyone if you feel you might know PLEASE help.