Hi Melinda,
I was always under the impression that if it was something your body was used to before you got pregnant, then you should be fine during pregnancy as long as you take it a bit easier.
So - if its using muscles that you were already using prior to falling pregnant, and your heart rate stays down beloe about 120-130, it should be fine.
Have you thought about getting into some Yoga? This is also apparently good after about 12 weeks to get into, and you dont have to have done it before as long as you have a qualified instructor who knows you are pregnant.
I know when I have done too much cause I get tummy cramps andI feel really sick, so I'd just watch out for those signs.