Oh I hate it when people are sad. I am sorry you are feeling this way.
Well in my humble opinion we do NOT know that oil causes acne. If that were the case, and the case were that simple, there would be no problem controling and or curing acne across the world. So don't completley discredit the derm. Although it doesn't sound as if the cleocin (is that what it was?)
is working for you, however I don't know how long you have been working with it. It usually takes anywhere from 2 to 4 months to see if something is going to work for you. This is what my derm tells me and I love him. He also says that if in 2 months my acne gets considerably worse, it isn't going to work and to add something into it or take it away. But if it seems to be stabalized then I must wait because maybe in 4 months it will be fine. I don't know how things are for you though, as I don't think you specified.