Skin problem ( pimples ) Any mark.

I am having skin issues from past 3-4 years ( white pus filled pimples ) . I had visited dermatologist several times . When the 1st time i visited the doctor prescribed me isotretinoin capsules , lip guard and clindamycin gel . I saw a deastical chnge My acne was gone in under a week , their was not a single pimple. i have continued isotretinoin for 3 months , all acne was gone then my doctor stopped the medicine . But unfortunately after 1 month my acne came again and was more worse I don't know what happened I was confused , So i didn't go to the doctor for several months then i decided to go and see another dermatologist . He prescribed me doxycycline 100 mg/ 2 times per day . My acne were improved but when i stopped taking antibiotics they came again . Now i controls them my using a good facewash and by maintaining a balanced diet . But my acne are still their like 3-4 acne daily not more . But my acne heals very quickly on their own within 2-3 days without any mark .