Are mid cycle dull cramps and sore breasts a sign of pregnancy?

YES!this could be a sign of pregnancy when your breast get sore then you usually are pregnant. The cramping feeling could be your fetis attaching to the uteris if the pain is early on. Later in the pregnancy it's your uteris stretching.

maybe not, It could also PMS, I think the difference in Sore Breast in pregnancy and PMS is that Sore breast in pregnancy have longer pain duration than Sore Breast in PMS.