I've been nursing for over a year now. is it safe if i switch to regular multivitamins from prenatal vitamins?

Yes: Summer, the primary purpose of prenatal vitamins is to make sure that the baby has enough folate to assist neural development. Regular multivitamins should be fine now. Make sure your baby is getting the right supplementation, though. Human milk tends to be deficient in Vitamin D and Iron. Speak with your baby's doctor about the right supplements. Hope this helps!