33 weeks pg. and am have had sharp cramping pains where it feels very tight belly gets harder . it last for a few minutes . are these braxton hicks?

Contractions: Yes, these are most likely Braxton Hicks contractions. Having some at 33 weeks is quite normal. They should not be regular and frequent though. You might have 3 or 4 an hour and then not notice any for the rest of the day - that's ok. However, if they are frequent, painful and regular, or if you see any bleeding, you should be checked by your doctor immediately.