Which medicine do you use? Benzoyl peroxide or tetralysal? I use these everyday and the effects take at least 6 months to start and can take like 5 years to go, but I have medium bad which was starting to get worse but now its much better, although I have alot on my forehead(which thank-god is covered by my hair) and on my chest and back (which is covered by clothes), so try ask your GP for these as they will have much more knowledge about the situation and your needs.
Also the food is complete rubbish, I asked my GP and he said it has nothing to do with food and he is a pretty reputable guy, I even NHS'd it and they said it has nothing to do with food just a horomone being produced too much ( I think testosterone)