Hi. If you are cramping as bad as you say you are around your 6th week then you should stop sexual intercourse until your baby is safely thriving.
Im currently 38 weeks and when i was around the same weeks as you i had menstrual like cramps which my doctor said was normal since my uterus was streching.
The last time i had sexual intercourse and orgasm i started getting contraction that were really close but werent extremely painful. Painful yes! but not to the point where i thought THIS IS IT!
Ask your doctor. Most likely they'll say that it's normal, thats what EVERY doctor says about EVERYTHING, i personally think but if you dont feel right about what your feeling its better to be safe than sorry.
I wish you the best and good luck to ALL!