Ha I made a YouTube video on this exact topic because your story sounds near identical to mine , or soon will be as I'll be getting married next year, Catholic wedding, giving a speech etc I won't link it here but if you want to see I can pm you. Either way the jist of it is practice, practice and more practice. Speak to your priest and get the readings in advance and go over them before the actual nuptials. Any wedding speeches that you want to give, write it using words you're not going to stutter on as much. I know the second part of my suggestion is avoidance, something we are stutterers shun in our community. While I do agree we need to embrace or stutter, I know how these big situations can be daunting and you just want to do anything you can to get past it, so in that case, use any technique you want I say. Practice daily, so you know what words to say, how to say them, when to take a deep breath and so on. Best of luck man!