is it abdominal muscle pain or is it stomach pain?
if abdominal muscle pain. then its normal. You are suffering from DOMS. give it a rest for a few days before continuing.
if its stomach pain. better get it checked. Most people train after heavy meals ended up with an actual health problem. (pankreatic ulcers, etc). no one should train immediately after meals. should have at least 1 hour rest before the actual workout.

i would say its ok to continue 2 days training and rest 1 day after that.....then only continue the next day

dun do situp, crunches is better since situp only work ur abs until certain limit and no matter how high u go, it still work the same part of ur abs n not other parts of the abs d (correct me if im wrong). it hurts the 1st few days but as u keep doing, u wont hurt anymore.

What are you looking to gain by doing these?