Freaking out. Please help.

So my partner and I have been having sex for a while now. We always use comdoms the correct way as our source of birth control. My last period was on time and normal but now, it's ovulation time. And all of a sudden things are getting wierd. We had sex yesterday and it wasn't any different than how we normally do but it was slightly achy at the end. When he pulled out of me the condom had a bit of blood on it and I had light spotting for a few hours after. Now today, no spotting but I am cramping like I am on my period... what does this mean, I've never had this happen before? I have a son who is almost 3 now. I have never experienced anything like this and so I'm freaking out a bit about what it means...

Thank you so much in advanced for your helpful responses. :) Hope all are well.