I am a month pregnant and sometimes after intercourse i will get cramping that's pretty painful but only lasts about 5 min. should i be concerned?

No: At only 4 weeks of pregnancy there's likely no harm that having intercourse can cause. Cramping, especially if you've had an orgasm, can be normal as well. I would definitely mention this to your ob/gyn at your next appointment, but for not i wouldn't worry. So long as not having any bleeding, you should be fine, but definitely speak with physician about it.