I've had many miscarriages and my kiddo. With my SON I had twitchy cramps throughout the first 4 months. Especially whenever I finally RELAXED. You know, been busy, sit down, and ouch... twitchy ouchy... weird. Around 4 months everything just started aching all the time. (Yay fun).
With my miscarriages (eveyone is different) I did NOT cramp until after I felt like I was going to passout. Like someone let water out of the bath... dizzy... blurry... couldn't think straight. I'd feel like I was on the edge of consciousness for a few hours and then the contractions would start.
My pregnancy with my son was so different from the others, it was one of the reasons I just had a feeling he'd pull through.