Hello,
It seems like you have new pimples quite frequently. In that case apart from topical treatment you may want to consider oral medicines such as oral doxycycline, erythromycin or even isotretinoin (a Vitamin A derivative) to minimise the occurrence of new pimples. The intense inflammation from pimples can lead to scarring so I always believe that preventing acne occurrence is important in acne treatment, apart from treating existing spots.
It is great that you are using a topical antibiotic (Clindamycin) to treat new pimple spots but an alternative would be Clindoxyl (clindamycin + benzoyl peroxide) to target the new pimples. Niacinamide has anti-inflammatory properties, you can either use it in the day or night, there is no major advantage of one over the other. A topical retinoid derivative such as Differin is appropriate for your condition, but may I suggest increasing the strength to tretinoin cream if you are able to tolerate Differin. This would bring about greater efficacy to prevent new acne and to clear up any comedones.
Do consult an experienced dermatologist who would be able to assess your condition and prescribe treatment.
Take care and happy holidays!
Best regards,
Dr Ker Khor Jia