Fell asleep with heating pad on belly

Im 15 weeks pregnant.
Last night I had a huge tummy ache with abdominal pain.  I put a heating pad on my tummy (on low) and accidentally fell asleep for almost an hour and a half (was only going to use it for fifteen minutes).
Would this affect my baby? Should I go to the doctor?  
I know I did a bad thing.  Any help would be greatly appreciated.