Menstrual-type cramps?

Superzuber

I was diagnosed with an irritable uterus about four weeks ago, which for me is a very tight belly for extended periods of time (like sometimes more than an hour) and it feels something akin to holding a plank position for a long time. They happen daily and are triggered by a number of things, which usually I can pinpoint. 

A new symptom started on Saturday on the three-hour drive to my SIL's house. I got what felt just like menstrual cramps in the lower part of my abdomen. That old familiar feeling I haven't felt in months. It passed in less than 30 seconds and it wasn't accompanied by a tight belly. I got it a couple more times that day and then maybe 8 times total yesterday. This morning I got three more in about an hour, the second one intense enough to sort of breathe through. I got up and showered, had a couple more in the shower, then went to a massage appointment, had a couple more on the table, then came home and called the labor and delivery advice nurse. Menstrual-type cramps are on the "When to Call" list. The nurse said it's nothing to worry about unless I get four or more in an hour (between the menstrual-type cramps and the irritable uterus contractions).

I have a couple risk factors for pre-term labor so I'm freaking out a little bit. Has anyone else experienced this?