I lost my first

I recently just found out I had a miscarriage and I never knew , Doctor didn't see a baby or even a heart beat I was suppose to be 12 weeks pregnant turns out I lost the baby back in March and I never knew I bled for 3 days but I thought it was normal since I felt no type of cramps no type of pain but it was a silent miscarriage I lost the baby at 8 weeks , I now find out same day that I could be pregnant again and the sac my doctor saw is in fact the new baby I got pregnant again !! I'm roughly 4 weeks pregnant I even took a digital test my boyfriend thinks it could be left over hormones still there giving me a positive and maybe that sac is the old one I won't know until 2 weeks when I go in for an ultra sound .... Wish me best of luck.