Can anyone help? Pregnant again?

Savannah • Happily pregnant with my 🌈👶🏼
Here is my story:
April 23- my doctor confirmed I was miscarrying after my hcg levels plummeted from the 360-380 range down to 120. I was almost 5 weeks pregnant.
As dumb as it sounds I didn't consider the fact that I could get pregnant again right away...so I continued have unprotected sex without a second though.
5 weeks since bleeding from miscarriage....I have still not received my first real period. My doctor told me to take a pregnancy test at the end of May if I still hadn't gotten it.
May 23-strong positive at home pregnancy test during the middle of the day. 
What do you think is going on? Could it take 5 weeks for my levels to drop from 120 to a non-pregnant range when I was only 5 weeks along? Or could I possibly be pregnant again? Of course I'm asking this question because the doctors are closed for the holiday weekend. Any thoughts would be appreciated.