Can You Still Bleed In the Early Stages of Pregnancy?

Hi all. Well...I recently m/c my baby @ 18wks, 7wks ago. I haven't stopped bleeding yet and I started bc pills (aviane) just 3wks after I gave birth. I had sex with my fiance', no backup method, 2wks after I started bc. The dr said to use backup for the first 3months, but I was being careless. I took a urine test at the dr's but it came out negative. Then the dr said it could still be early. The thing is, i'm still taking the bc pills as directed by the Dr. Since my urine test came out negative, that means that my hcg is all out and that I could've ovulated around the time that i've been having sex without backup methods. Could I still have gotten pregnant then? It's weird I know, but i've been experiencing frequent urination, slight nausea, fatigue, increased appetite, breast enlargement, a little dizziness, all are similar to what I experienced with my pregnancy. I'm not sure if that's the case or if it's the bc. I'm still spotting and bleeding lightly. The dr said to retest at home in 2more wks but I want to know if I could be pregnant? I would love to have another one, but the dr said he didn't want me to get pregnant so soon after the m/c. Says my uterus has returned to normal size too. So could I still have gotten pregnant and still bleed? I'm starting to lighten up more now, it seems like it's coming to a stop now..Any help would be very much appreciated!! Thanks.