I can relate to this problem, because I had acne too. I kept on getting creams from my GP and nothing was working, no matter how strong the cream was. Here's what you do, there's one word that could change your life, as it has done mine:
Roaccutane. Mention that medication to your GP, and see if you can take it. You can't get it prescribed from your GP, but only from a dermatologist. Nevertheless, ask them about it.
I took Roaccutane for 6-8 months & my skin has been clear since. I don't actually have to wash my face at all, except I only wash it when I go into the shower. I've had about... 2-3 whiteheads since I came off the treatment, and they vanished within a couple of days anyway? Mind you, the treatment finished around mid last year. You can see that around 10 months has really done something. You don't feel the full results either until 2 years on apparently.
They'll ask you to take blood since the medication is somewhat dangerous. I actually went through hell during my medication, since it gives you severly flaky skin/hair & really bad chapped lips. You just have to cope with it, and it worn off for me after I took the medication in a matter of 2-3 weeks. The side-effects are seriously dangerous, I must warn you about that.
Ask about it though:
http://en.wikipedia.org/wiki/Isotretinoin
That's basically all you need to know about it + includes the side-effects. It's got many names but in England, Roaccutane is the name. I'd seriously consider it, since a couple of months actually helps you for the rest of your life. Yeah, that's right, I'm 'cured' of spots.