light to med cramping

my hubby and i are ttc number one so im new at just 'doing it' without anything on him. we've been getting busy for 6 days and yesterday i began to notice that im cramping up almost as if i were about to get AF~ but less intensely. also have mild back pain in lowest region. my fertile window is now and i am ovulating day 3 right now.

any clues as to the weird cramping ? no prior cramping after sex for 7 years together. thx everyone. sry if TMI in any way.