I’d like to second what kiala2021 said – it’s usually pretty hard to tell whether something CAUSED vaginismus or that it just REVEALED that it was there. There’s a lot we just don’t know about that (although I have read that some women are just predisposed to having vaginismus – it can be as simple as because you’re prone to anxiety and you carry that tension in your vagina).
I think something about your story that a lot of people will recognize is that a lot of women who have vaginismus have negative experiences with tampons, but this isn’t usually a tipping point for them as there’s such an easy and painless alternative in the form of pads, so most women just decide they won’t use tampons. Once they try to have sex later is usually when the actual emotions and challenges of vaginismus have to be confronted.
At any rate, it’s good that you know what situation you’re dealing with and that you’re waiting to start therapy! Let us know if you have any questions – I’m glad you’ve figured out what’s going on and are seeking help!