My 9 month old has been having loose stools every 20-30 minutes today. Every time he eats or drinks something it comes right back out and now he has a bad rash because of it. I'm keeping plenty of ointment on his rash but what can I do for his stomach? I feel bad for him because I know he isn't feeling good

Also any tips on a bad diaper rash? He's really pink and just screams anytime i put something on it..he's never had one this bad. I've tried a baking soda bath, a&d, butt paste, and desitin but nothing is working