Please, help!

Hi ladies.

Here’s what’s happening: my husband and I had sex on the 6th and the 9th. For about a week now, I’ve been “spotting” (I think), light enough where I don’t need a pad or tampon, but heavy enough where it’s there every single time I wipe. Sometimes it’s bright as if it’s fresh blood, sometimes it’s dark as if it’s old blood. The day before yesterday, the lower right side of my back started hurting. It doesn’t hurt if I push on it, but it does hurt if I move a certain way, if I bend over, and if I cough (but not if I sneeze, which is weird). I had kidney stones about 4 years ago, which is what I thought this pain might be related to, but now I’m not so sure. Googling all this has been next to no help, so I thought I’d ask on here before going to the doctor only to find out I “pulled a muscle” or something dumb. I’m supposed to start my period on the 17th, but I don’t think the pain I’m having currently or the spotting is related to that. Any and all help is welcome and appreciated. I’ve been laying on a heating pad and taking ibuprofen but nothing is really helping.