fecal incontinence i need help please!! :(

Hi..I'm Faye owner of 6 cats..I love my cats soooo much...but recently I have this terrible problem that I really don't know what to do anymore. My one year old cat became a part of my family  when she was just a few months old..but we discovered that he has a fecal incontinent, we kept on giving him Lomotil (Diphenoxylate and Atropine) because we thought that it was just a very simple diarrhea, and it brought a temporary relief. However, after a few weeks it came back again and we thought that it was just okay, that it will just disappear but it became worse. What makes it even sadder is that my other 4 cats were also infected, I really thought that it was brought about by parasites so I decided to bring them to a Veterinarian nearby. The vet said it wasn't caused by a parasite but by a bacteria (e. coli) so he gave them antibiotics (cotrimoxazole) for 5 days. Unfortunately, they are still not well until today I also discovered that their third membrane is now already visible and it worries me a lot, but apart from that they look very healthy,they eat well, they play and it looks like nothings wrong with them except for the fecal incontinence part. Please help me..what should I do?I am really worried and right now my mom is already very mad at me that she wants to throw away all my cats and i don't want that to happen. Please tell me what to do..:(..any suggestions, or information would really help me a lot..:) thank you so much..