Place kitten with his or her mom. You are probably doing more harm than good. Provide a nice, quiet warm space, and let momma cat do the rest. I am sure she's not happy. 3 kittens is a small litter, so mum has plenty of milk provided she's being fed high calorie nutrition ie kitten food. My guess is that your intervention is causing baby to get a lot of air into it's stomach. If it's I'll appearing, my guess is aspiration pneumonia, due to improper bottle feeding. Go to the veterinarian, or at least call one. While reluctant to give advice, they can at least educate you regarding basic needs and care. In the future, if you want to help, not harm, do your research. There is no shortage of amazing forums, blogs, vlogs, subreddits, web sites developed by rescue careers, etc. There is a wealth of info out there if you just simply try. I hope the little fuzz all makes it through Please DO NOT ADMINISTER ANY DEWORMER TO MOM OR KITTENS UNTIL THEY ARE FINISHED NURSING AND KITTENS ARE 8 WEEKS. Also, no home remedies, for the love of kitties.