Talk to Gynecologist on Difficult

Is it possible to have periods like bleeding and still be pregnant.

I had positive pregnancy test in strip and after two and half weeks i am having periods. Didn't get the time to go for beta hcg. Had an ultrasound yesterday in which no gestational sacs were observed meaning i wasn't pregnant. I am so confused. The pregnancy strip test can be wrong? It worked for me in my first pregnancy. I have doctor's appointment next Thursday