On and off cramping at week6

This can be normal. For my case due to my history, I was put on duphaston on week 5 onwards. I was to take it 1 tab 3 times a day and gynae told me to come back if brown discharge appears. 5 days later I had brown discharge and went back to my gynae, he increase my dosage to 2 tabs 3 times a day and the discharge stopped. If you feel uneasy, you can just visit a gynae to ease your mind.