Avoiding pregnancy for 6 months only.

I'm getting married in September and want it get pregnant immediately after. I don't want to get pregnant before and be pregnant on my wedding day! My partner doesn't want to use condoms, and I don't want to get back on the pill because I want to start trying the night of my wedding :) We've been using withdrawal and monitoring my cycle with Glow. For instance, he might come inside me when my chance of getting pregnant is only 2.3%, and never more. I know this isn't 100% foolproof (and if we get pregnant  it'd still be a happy event). Would love to hear your thoughts on this approach. Thank you!