Contractions

What the heck do contractions feel like? I'm only 28.5 weeks so they're really just Braxton Hicks, I suppose. But I'm so confused. I was having sharp pains in my abdomen that would make me double over and I thought they were contractions..then I went to my doctor and he said most women compare them to a "dull, throbbing, menstrual cramp". So now I'm so confused and just want to know what to be paying attention to and when the heck to start counting.