OP - how far off is your derm appointment? I suffer from acne - since being a teen though. The only sure fire thing to keep mine at bay was Dianette (which I am not allowed to have, as I am 45 and have a blood clotting disorder.. sigh).
However I was referred to a derm at the hospital. Typically my skin was okay(ish) and the most he would do was prescribe me Differin Gel.
He did say that if the acne worsened (which it did) to go to my GP and request prescription for Trimethoprim, which is generally prescribed on a short term basis for cystitis. The GP did prescribe this as he had stated it in his letter back to them following my appointment.
I did take it for about a year - they are quite strict at blood tests to ensure that your liver etc is up to it. And I guess it worked to a point - in conjunction with the differin gel. Still have the oiliness though, which I hate.
Read up on Roaccutane before you go for your appointment. It may be that your acne is 'bad enough' for that. y It is what I wanted really, but at the time my skin was no where near bad enough. At least if you know the ins and outs of it first, they may discuss it with you. I believe it is effective in adult acne - long term, v low dosage.
Also, enough though I scoffed at the idea, diet can play a part. I find that when I am tee total, and avoid sugars my skin can be better. Apparently the alcohol affects testosterone - which can be a cause of the oiliness.