Hey! First and foremost, apologies for going anon - people IRL know my account on here and it's not something I would openly discuss with them.
Obviously, I can only share my own experience and my knowledge is nowhere near that of a medical professional, but I've tried various treatments over the last two years of having acne (I'm 16 now.) Generally the treatment you have depends on the severity of your acne and what you've already tried.
It might help if I tell you what I've been treated with so far. I started in June 2012 (approx.) on Duac Daily Gel for about a year. As my acne began to worsen slightly, I was prescribed Zineryt from June 2013-December 2013, at which point it stopped working I went onto Differin cream + Lymecycline (an oral antibiotic), a common combination for moderate/persistent acne. By the sounds of it, you may have been prescribed this already but if you haven't it could be the next combination, or possibly another antibiotic (there are lots of types of antibiotics) with another topical. Other topicals include Tazorac and Azelaic Acid but I have no experience of these to share. Personally, the Differin+Lymecycline treatment made my acne so much worse that I was referred to the hospital dermatology unit and I started isotretinoin (Roaccutane) on the 5th August 2014.
As for my experience with Zineryt, I was mostly pleased with it. I saw decent results but as with all antibiotics (Zineryt contains Erythromycin) the bacteria became resistant to it and I had to stop at around 6 months. I wish I had stopped it earlier because I could have avoided its worsening, but I wasn't to know. At 8 weeks you should be seeing some improvement, but everyone's skin reacts differently and you may not see any improvement until much later, so don't lose hope. Often it gets worse before it gets better but if it gets significantly worse it's worth seeing your doctor about it, as this could mean the treatment isn't working, at which point it's advisable to change treatment.
You mention seeing the dermatologist: due to budget/staffing constraints, specialist NHS dermatology units are stretched to the limit with patient numbers, and acne is considered only a cosmetic issue (it's not, I know) in comparison with life-threatening skin cancers and such. Therefore getting a referral on the NHS is pretty difficult, and requires you to have tried at least one antibiotic with a topical for at least 6 months with little to no improvement. If you do get a referral, you'll be considered for Roaccutane, which is by far the most effective acne treatment and perhaps the only to offer long-term significant improvement and often curing of acne in a considerable majority of patients - my dermatologist that it's one of the NHS' most successful drugs of all time. Some of the transformations are something to behold, but with fairly hefty side effects the drug is reserved for those with severe acne or those who have tried lots of previous treatments without success. There are jumps to jump through too: blood tests, monthly hospital appointments and for females a monthly negative pregnancy test due to the drug's high teratogenicity. Regardless, if your acne is having a psychological effect on you then it's an option to consider, if not for a couple of years down the line.
I would recommend you make that appointment around the 3-month mark to discuss options with your GP. After all, only they will know how bad your acne is and how much it has or hasn't improved - something no one on this forum can decide for you. There is a plethora of information on the internet, some useful and some wildly incorrect, and lots of support, so don't feel alone. Acne is a horrible, horrible disease that goes way beyond being 'just spots' but with the correct treatment you will ultimately achieve clear skin.
Sorry for the mammoth post, but I hope it was helpful