What could this be/mean?

My hubby and I had sex tonight, the "fit" was a lot tighter & a tad painful more so uncomfortable he seemed to touch my cervix easier. We both climaxed but after I feel cramps in my lower back & uterus. Past week I've had the backache somewhat & I have had some fluttery or twitchy type feelings in my lower abdomen also... I've been pregnant before but I'm not convinced that's what this is... Anyone else ever have this happen?