I think i got a yeast infection from my uti antibiotic. should i wait to use monistat until i'm done with the the antibiotic or can i use it now?

No need to wait: You can start it any time. However, best to first discuss it with the doctor treating your UTI. Also, you may want to consider oral fluconazole (Diflucan). A single pill by mouth is just as effective as a few days of vaginal Monistat or other creams. It's also available over the counter. Many women find it more convenient. Good luck.