Something is wrong..

The last day of my period was jan 7 and i had sex on mu fertile days a week after our days of BD i starded lightly lightly bleeding it turned from dark brown red or light pink red and then it was completely gone. It lasted 3 days. I though it was AF so i took a herbal tea to help it come. Buy nothing happen i missed the actuall period so i took 2 pregnancy tes and they were positive. But now everytime i do alot of moving or walking i start bleeding again and when i lay down and stay still i completely stop bleeding idk whats going on!!!