Awww hun, you're not a bad mum!! Oskar had a horrid nappy rash for about a month a while back - every time it looked like it was clearing it would suddenly just come back with a vengeance!! I think it actually was related to him teething and he'd been sick with a throat infection also. Anyway, I had been using paw paw ointment but this didn't work, also bepanthen (my friend swears by it) but it wasn't working so I tried Amolin and I smeared it quite thick on EVERY nappy change and it worked sooooo fast it was amazing. I now put it on every night after his bath and any time there's the slightest bit of red on him and it seems to get it before it can become anything. It's not very expensive either!!