will exercising too much cause early labor?

Not necessarily. It all depends on how much you exercise regularly. If your body is used to it then you should be okay. If you are exercising and notice that you're having some stomach pain or discomfort at all, stop. If it goes away and doesn't come back, go ahead and keep exercising, just cut down a bit. If it doesn't go away drink 3 glasses of water, empty your bladder and lay down. If it doesn't get better after an hour call the hospital and tell them about it so you can go in and get checked. Then really cut back on exercising if you're even allowed to after that. I was jogging and it caused me to contract a bit, but it went away as soon as I stopped. I switched to walking, but now I don't do anything because whenever I do I start contracting. It all just depends on your body and what you can handle. You'll know what to do.