Kitten Help?

I just recently got a kitten, He is now 4 months old... For some reason hes been having crazy diarrhea and I'm not sure what to do. Ive tried to give him pumpkin and it didn't seem to do much help, i just started him on probiotics the other day, and today he had pop so bad it got all over him.. Not sure how he managed that. Vet is closed right now, Advice? Anyone with experience? 

Is he eating and drinking ok? Active happy kitten otherwise? I'd be visiting the vet as soon as they are open. Hopefully someone else can give you advice that will help in the meantime until you can get to the vet.

He is acting completly normal. Very active. He doesnt drink alot, but i feed him wet food, i water it down a bit so he can get more water. I ive him good food, no proccessed meat or grains. He also doesnt et any table scraps. The only reason i would think he is having issues is the old owner fed him really bad food. 

He needs to get to the vet to rule out parasites.  It often takes more than one deworming to completely rid the body of the parasites.  Then, look at his diet.  He should be on a high quality canned kitten food and have access to kitten dry food all day.  They have such high metabolisms as kittens, it's insane how much they need to eat.  What you're feeding him may be too rich for his system and he's letting you know that.  What was he eating prior to you adopting him and exactly how long has he been on the current food?

He has been dewormed. Before he was eating really cheap food she gave me the rest of the bag an i found out its expired.... Hes been on his new diet for about 3 weeks, its Cat in The Kitchen wet food, and wellness dry food out all day

Due to the life cycle of the parasites, it often takes multiple treatments to completely rid the body of the parasites.  He could also have tapeworms, which require a separate treatment.  I would ask the vet for another fecal to rule that out and get a tapeworm treatment.  Then, you need to look at his diet.  It could be the food is too rich for him.  If you changed dry food abruptly, that will result in upset tummy and diarrhea.