Maybe just maybe...

Hello, I was wondering if this happened to anyone else. I had sex with my husband three nights before my expected period was to start. Shortly after intercourse I notice a lil brown pinkish discharge and then the next night it was like I started early. But... Then my period if that's what it was, only lasted three days and not my usual five days that I always have. So could it have just been implantation and I could be pregnant? And I did only cramp that first night then I had no cramps, I'm just really curious that this if the first time I've had this happen. Please help if you can :)