I am on day 6 of a 10 day course of antibiotics. Now I have a yeast infection. Can I treat it now or should I wait to finish the antibiotics?

Can start now. Some tx options include vaginal cream, ointment or suppository for sev. Days (7 to 14 days sometimes). Otc meds include Monistat (miconzole), vagistat-1 (tioconazole), femstat (buoconazole), Gyne-Lotrimin or mycelex( clotrimazole). Diflucan (fluconazole) (oral antifungal) is taken once.
Start now. It is ok to start treatment now but it may not resolve completely until the antibiotic is finished.