I feel like if you're that catastrophically bad at putting things into words, the best option would be to read a bunch of love poetry or song lyrics until you find something that resonates with you and make the vows essentially just "To borrow a quote that always really stuck with me: [insert appropriate Shakespeare here]."
You're still using someone else's words, yes, but you've at least given credit instead of pretending it's yours and you've shown that you have actual emotional investment in this.
Fuck, just repeat that passage from Corinthians everyone uses, if you must. It's good writing and unimpeachably traditional, there were so many other choices here.
[insert appropriate Shakespeare here]
."