Does taking vaginal antibiotics decrease the effects of primulot n? i took 3 clindamycin while taking them and got my period! can i be back on pills?

Most likely no: There is little evidence to support that antibiotic significantly impact hormones.

It's possible: There are some reports that Clindamycin, even used vaginally, can decrease progesterone levels which might promote breakthrough bleeding. Primolut N, a synthetic progesterone, is most often used to manage menstrual disorders including irregular periods and to delay menses; it is not a contraceptive. I would continue the Primolut but consider an alternative if you need vaginal antibiotic therapy.