Contractions

I'm on bedrest and I've still been having contractions while on my medicine to STOP them. Anyway, I'm 33 weeks and I just had a contraction that wasn't necessarily PAINFUL but it DID hurt. And it felt like he was pinching my insides, and it just kept getting tighter and tighter and the pinching got worse and worse. So I'm wondering...what does an actual contraction feel like...like when you're having the baby...I know the pain is more in your back, but do you still get the pinching?