Should I go to the doctor?

I had sex in one of my fertile days, probably a day before ovulation. Although, my period is not that regular, but I wasn't expecting it until next week. Since yesterday, I started having bad cramps but not my normal ones. It was my back. It was as if my was gonna come off my body! Went to bed thinking I will wake up having my period. But that didn't really happen. I spotted all day. And now I have this pinkish period and no cramp like I usually have. I usually have really bad ones. I am not having bad ones but my back is still aching but not as bad as earlier. I can't sit for long or stand for long. Anyway, I have never been pregnant and want to be. It's time I have a little one. But could it be that I am despite that light bleeding? And I also had pain in my body yesterday as if I was having flu-like symptoms but I have no flu.