Miscarriage.... Pregnant again?

Ok so I miscarried dec 5 (medication induced) I took a pregnacy test to see if my hcg hit zero. It was VERY positive. I figured my hormones weren't responding well. Called the dr. She said because I had unprotected sex ONCE!  I could be pregnant AGAIN!!!  I haven't even had a normal AF since the miscarriage. The dr is checking my levels to see if they will double. Has this happened to anyone. I don't know if I'm ready to be pregnant again. I would be so happy but I am still grieving. Please help!!!