I had the exact same thought a few days out from surgery! When I had my follow up with my surgeon, he explained some of the bulging was due to the type of staples they used to close the stoma... I am 4 months out and my scar has flattened out completely. I would be sure to ask at your next follow up to be sure it is not a hernia.
The best advice I can think of is to listen to your body!!!! Every single person is different, so your journey and recovery timeline will be different as well. I found myself trying to compare to people who were healing "faster" than me and I quickly learned that does nothing to help. Your body will guide you on what you need to do, so do everything you can to be patient with it (meditate, find support, scream into a pillow...). This journey sucks, but you can get through it. Don't be afraid to ask for help and speak up with your medical team. Best of luck!