Kitten Tummy Troubles

Hi! I'm new to the site and was wondering if anybody could give me some suggestions.  My 3 month old kitten, Sophie, has had diarrhea for the past 5 days and has been a little gassy. She's drinking water, eating, and acting like her normal, playful self, other than the litter box issues. I've tried feeding her boiled chicken and rice, as well as canned pumpkin, but neither made a difference.  I'm planning on taking her to the vet when they open tomorrow, but I was wondering if anybody had any ideas or suggestions/experience as to what could be making her tummy upset for so long?

Some background: Sophie was adopted from shelter and she is a FIV+ kitten. She's up to date on all her shots, has been dewormed a few times before, but has had a flea problem recently and is on Revolution for it.  I did change her food from Authority to Chicken Soup, but I've spent the past several weeks transitioning her onto it (since she had pretty bad diarrhea when I first got her, from switching her food too quickly), so I don't think her food is causing it.  I really want to get my kitty back to 100% normal ASAP!  Thanks so much!

I think since you've already tried the chicken and rice trick and it didn't help, and you KNOW you've got a flea problem, it's probably parasites that are causing her issue.   Hopefully when she sees the Vet tomorrow they'll be able to get her started on something that will kill those little internal buggers (assuming that's the issue)

Thanks so much for your help! However, Sophie is back to normal today.  I checked her litter box this morning and it seems that whatever was causing her to have the diarrhea has finally resolved itself.  Thanks!