Tetracycline has its limits, I think that its biggest benefit is reducing the inflammation. It is not effective if it is used alone. Your doctor should combine it with benzoyl peroxide wash or lotion and a topical retinoid.
How bad is your acne? Is it only on your face?
I wouldn't pressure your doctor to prescribe accutane. It's complicated and you don't want to spoil your relationship.

If your showing no improvement from utilizing the tetracycline family (minocycline, doxycycline, tetracycline) then I wouldn't recommend continuing their use. Unfortunately, in recent times physcians have ignorantly prescribed antibiotic cycles too often for patients that periodically were suffering from an ailment that honestly didn't require antibiotic treatment. Due to this practice we have begun to drastically increase the prevalence of various antibiotic resistant bacteria. It's been documented that there have been frequent encounters with mutated versions of P. acnes bacteria that displays a moderate resistance to the traditional pharmaceutical compounds typically provided for acute/chronic development of acne vulgaris.

Here is a good summary detailing this epidemic. http://www.skintherapyletter.skin.ca/2012/17.9/1.html

Always try to include probiotics when taking antibiotics to promote the growth of beneficial bacterium that inevitably is destroyed along with bad bacteria from various antibiotic families.

I remember you were the guy that started tetracycline the same day as me at the same dose. I have the same problem. it hasn't helped me at all so far and its been almost 2 months.