pregnant right after a miscarriage

Ladies, I am wondering if I am pregnant again right after a miscarriage with my twins or if it's just old hormones but it looks to me like the lines are getting darker. I'll find out in a couple days when I go to my ob follow up appointment. I miscarried my twins 6 weeks ago but I chose to give birth to them in the hospital when I found out I had miscarried 4 weeks ago. I'm also wondering if women have conceived while still postpartum? My boyfriend and I have had sex multiple times and ever since then my bleeding had stopped until a couple days ago when we had rough intercourse(it's been a while) and now I have light bleeding. The last test I took was the expensive one but I wasn't really paying attention to the time so I'm not sure if it's the evaporation line or an actual line. Maybe I'm pregnant?