Acne doesnt go away.. why??

I was diagnosted with adult acne originally in 2004, I was 28 years old.. no doctor could tell me what exactly triggered (I was surprised because as a teenager I never had acne).. after a mix between doxicycline and monocycline for one year, the acne dissapear.. for only two years.. and when it came back on 2007, it was stronger, bigger pimples (2 or 3 heads on each one) impossible to pick on them (it seems to be really underneath the skin).. and more frequent, monocycline and doxicycline dont do anything for me anymore.. my current dermatologist, who at this point Im starting to believe he doesnt know what he's doing (sorry about this to all the docs here but I dont know what to believe anymore) has been prescribing solodyn 45 mg (I only weight 120 lbs) for the past TWO YEARS.. continuosly.. I am afraid this might have a side effect, he hasnt asked for any type of blood work to see how my liver is doing with all this medication (people scared me with the side effects of acne pills) and the acne, even though it seems to improve from time to time.. every 3 months, it becomes stronger.. dermatologist creates a new mix (maybe going back to monocycline) and then the cycle continues..
Also I apply every night.. differin gel 0.1 % and also in the morning.
I need help.. does this sound right?? Im concerned it has been 2 years with prescription medicine.. and nothing.
I exercise regularly, eat healthy and work inside an office.. am I missing anything here?? why the acne doesnt go away??
Thanks,

[loiloi]

Hi. Solodyn contains Minocycline and is often very effective, especially when used in conjunction with a topical retinoid such as Differin (adapalene 0.1%).
If the above regime results in failure or relapse after a fair trial, you may be a candidate for Oral Isotretinoin (Accutane/Roaccutane). Has your dermatologist discussed this with you?
If you are female, have you tried Diane35/Dianette (a special contraceptive pill for acne)?
Acne occurs when the patient has high levels of androgens or a particular sensitivity to the effects of androgens. Unfortunately, a healthy diet and excerise cannot clear acne.
Eloise.