I think my son has a tummy ache...

What do I do. My mom watches him during the day while I work from 9am to 3pm and we have this mutual understanding that I feed him his foods during the day and she will just give him bottles when I'm not home so I feed him breakfast at 8am and ill feed him again around 3:30 when I get home and again around 7pm at night for dinner. Well today for some reason my mom decided to feed him breakfast and lunch and didn't tell me until I already started feeding him lunch and I had already fed him breakfast too so now he has eaten 4 times today and he's kinda fussy not wanting to lay on his belly... if it really is a tummy ache is there anything that I could do for him???