Why Causes Sore Breasts And Premenstrual Cramps Post Menses?

I had a normal period which started on the Wed 30th/Thursday 1st July, lasted until the following Wed 7th, fairly heavy

On Friday 9th I started with really sore boobs and period type cramps ...which I though was odd, last time we had sex was Sat 26th which was with a condom as normal.

I really really don't want to be pregnant ...so am I imagining it ...what is the likelihood that I am?

Next period due any time between the 24th & 29th July.