Light cramping? Constipated?

I’m getting some very light cramping, I’m not really sure if it’s cramping or just some tingiling. When I try to use the bathroom I really can’t and I can only pee, am I constipated? It feels like I want to but I can’t. Background is - I had sex at the end of September so 6 weeks go. I tested for pregnancy at 4 weeks after sex so it was a negative, so I don’t think this has anything to do with pregnancy, but I don’t think I’ve ever experienced this? Was this because I ate too much?