scared to have sex now

So a couple weeks ago me and my SO were having sex and after we were done he realized there was blood everywhere and I started my period (even though it wasn't due for another 5 days). After a week of AF leaving, it happened again! We were having sex and I start my period again! So to sum it up I have had two periods in the course of three weeks and both times I have started during sex. Is there something wrong or is this normal????