Blood during sex

I've been spotting off and on lately. Last night while in the middle of sex, I started bleeding. I thought it was my period (but that's not due until next week) so I put a pad in and went to bed. I woke up this morning, there's no blood in the pad. I've been wearing a panty liner all day today, and there's no blood in it as well. I'm freaking out because this has never happened to me before. Has anyone experienced this before?? Should I make an appointment with my GYN?? Please help!