My son is 1 these past 3 days he has been pooping back to back like 35 times a day & it's like a mustard yellow. what's wrong with him please help.

Stomach bug - viral: Likely a stomach bug. Due to the frequency of the stools you should really get him assessed by his doc to make sure that he's not getting dehydrated. Dietary modification for a couple of days is likely needed. Speak with your pediatrician.

Stomach virus...: It sounds like your son may have caught a stomach virus (such as rotavirus); however, at his young age and with that large number of stools I would recommend that he be seen by his pediatrician-mainly to ensure that he is not showing signs of dehydration and that his electrolyte levels are normal. It is important that you keep up with his output with an electrolyte solution such as pedialyte.

Look at his diet: Change in stools for a toddler could be for a variety of reasons but many times this can come from a change in diet. Review his diet over the last 5-7 days in regard to changes as well as increased juice or sugar intake. This age is prone to Toddler's diarrhea which is frequent stools not associated with infection and more due to his diet. Also viruses will cause frequent stools, both resolve.