It's totally normal for your baby to stop moving as much in the last few weeks. My doctor says they "run out of real estate". As for the cramps... I'm not sure, could be a little Braxton hicks or maybe your pelvic area is just adjusting for birth.
Could be that baby is dropping lower into your pelvis to get ready for the big day, which could explain less movement as its tighter on the uterus down there. If you are really worried go get checked out, it's always better to be safe then sorry. You're almost there Mama!