Formula Allergy ??

So my son is 9 months in a few days & for 3 days now , EVERYTIME he passes gas he pops (a picture is added of what his poop looks like every since time) . 4 days ago I let him have some apple juice diluted with water , but he only took a few sips & was not interested in it after that . I was also letting him eat a little bit of everything I was eating since he has 3 teeth now , but I haven’t been giving him anymore of my food since these poops started on Thursday night . So I know it’s not solid food causing this cause it would have stopped by now .

(Picture is pulled off of Google since I have yet to get a picture of it , my sons poops are more of a dark military green though)

He also has this extreme rash on his butt that’s a strawberry red color that I can’t get rid of , I think it’s because he poops so much . Diaper rash cream (Destins Rapid Relief) doesn’t work with this rash & usually works for him when he has a diaper rash . So I’m not sure if his poop is acidic & causing the rash or if it’s just a really bad diaper rash that won’t go away or what . But I feel lost & confused & helpless cause I can’t help him & he screams in pain everytime I change him .

He doesn’t spit up after feeding so I’m not sure if it’s an allergy but I just don’t know . I’m scheduling him a doctors appointment for Monday afternoon or on Tuesday , I just wanted to have some opinions on what it could be or what I can do .