Please help!

Hi guys, I’m a bit confused. I had my “period” from May 18th thru May 25th. I’m still spotting. Yesterday I took two test and it was positive. I went to the ER cuz I was concerned of the bleeding. They weren’t really helpful but they confirmed that I am pregnant. But I don’t understand how that could be possible. Has anyone gone thru a “period” and was pregnant?

Since the hcg level is too low for an ultrasound, I have to wait for 2 days and do more bloodwork 😩😢