I need advice!

So I have been out of work due to terrible morning sickness and cannot go to the vet right now. (My husbands paychecks are only just covering our bills) I guess I haven't been paying quite enough attention to one of my three kitties with all of my sickness and I feel terrible. I was looking at her today and noticed she looked really skinny and when I went to give her a bath she had scabs on her back right by her tail and her meow sounded like she has a cold. My husband also said one of the cats has been pooping outside of the litter box but I assumed it was because of him not doing a good enough job of cleaning the litter boxes since I can't because of pregnancy. Could this be related? We changed her food before I got pregnant because the stuff we were giving her before was making her throw up. I'm just so upset because I have six dollars in my bank account and I can't do anything about it. ( I know it's not worms or fleas because I treat her regularly with revolution.) I also want to say that her shots are a little behind but all of our cats are strictly indoor cats and we plan on getting them once I go back to work. I feel like a terrible cat mom. 😭