Mazal tov on your recent marriage!
Please consult with your physician to confirm that you are having yeast infections and to seek appropriate treatment.
While we can not definitively rule out yeast infections being caused by immersion in the mikveh, it is unlikely. Yeast is present in eveyone's body. An infection is caused by overgrowth of yeast. This can be caused by wetness in the area, scented soaps, or wearing nylon undergarments that don't allow the area to breathe. Douching or excessive cleaning is also a possible cause.
We do recommend that you reduce the number of bedikot during the clean days to the hefsek taharah and one bedikah on each of the seven days, to reduce the chances of irritating yourself. Change your underwear frequently if you experience regular discharge that leaves your underwear damp. Do not douche, and only clean your vaginal area with unscented/gentle soaps. You can also ask the mikveh attendant to make sure the mikveh is well-chlorinated. Make sure to dry yourself well after immersing, and don't go home in damp underwear or clothing.
We hope these suggestions help alleviate this problem. Please feel free to get back to us with any further questions.
B'Hatzlacha!