Hi. Acne is a chronic problem and may run for years and decades in certain individuals.
Acne is not necessarily confined to teens and can persist into third or fourth decade specially in females.
Acne in females could be hormonal. I would advice that you 
consult a dermatologist if your acne is not responding to traditional anti-acne medication.
If i was your treating dermatologist i would have advised certain blood tests like s.
testosterone, s. DHEAS, S.LH, S.FSH and pelvic 
ultrasound to look for 
polycystic ovaries, that might suggest if any possibility of underlying hormonal abnormality.
Along with that i would like to know your menstural history if any irregularity.
Treatment of hormonal acne is somewhat different than what you have been using till now
Apart from this general measures like 
weight loss and living an active life also help.
Hope you find my answer useful.
You can follow up with your dermatologist for more information regarding this.
take care.