I have had 3 miscarriages in the last 2 years. I just recently had a D&C done (11/25/0

and now I'm pregnant again. The doctors have been monitoring my HCG levels and they aren't going up very fast.
1level was done 12/31/08 3531
2nd done at a different lab it was 3095 01/02/09
3rd was 3475 on 01/05/09.
The doctors said they would be a difference in the HCG levels due to being at two different labs.
I go in today for a trans vaginal ultrasound and not sure why. But the dr. says it important.
The reason I am on here asking what is going on , is because i can't seem to get any answers and i'm very frustrated. I don't know how far along I am due to the fact of getting pregnant so soon after the D&C and i didn't have a period. Can anyone help me or give me some info. I don't understand how i can have a perfectly health 4 year old and now i keep having misscarriages.