Abdominal Pain

Eversince i decided to bring my core workout “beyond crunches” and tap into the realm of medicine balls, jacknives, etc, I’ve been experiencing abdominal pain 2-3 hours after the workout. I don’t know if it’s just muscle soreness but the pain is always accompany by an acid indigestion. Most of the time i have to take some form of antacid and it will subside eventually. I’m curious as to if this is just the soreness and pain that i get from working out or am i doing something improperly?