Hi.. Welcome to HEALTHCARE MAGIC.. I have gone through your query and can understand your concerns.. As per your complain pimples is a recurring skin condition and can occur due to a number of causes like oily skin, clogged pores, bacterial infection, inflammation and excessive sun exposure.. Dark spots left after healing of ulcers seems o be due to Post Inflammatory Hyperpigmentation. The medication Clamycef contains active ingredient Clindamycin and is effective antibiotic in treating pimples.. Isotretinoin is a retinoid and is commonly give to treat acne but should be used only under supervision of a Dermatologist.. I would suggest you that along with taking oral medication you should also start topical treatment like washing your face with salicylic acid containing facewash.. You can also apply a combination of creams or ointments containing Clindamycin and Benzoyl peroxide.. Yo can apply Adapelene gel at night.. For dark spots you can start applying depigmenting creams containing Kojic acid, glycolic acid, arbutin and Vitamin E.. Exfoliate your skin twice a week using a gentle scrub.. You can also do cool compresses over pimples.. Avoid oily food and drink plenty of water.. You can also go for treatments like Microdermabrasion and chemical peeling. Hope this information helps.. Thanks and regards. Dr.Honey Nandwani Arora.