I guess what I mean is doing the opposite of what your OCD wants you to do. So, your OCD wants desperately for you to find reassurance, "confidence" as you say, of being 100% certain that you have not made this vow. Therein lies the key problem of OCD. Whatever issue it is, we say to ourselves, "If only I knew FOR SURE....! I could be happy!" The problem is that, with whatever particular obsession we are struggling with at the time, we are craving an amount of certainty which is impossible on this earth. OCD is "the doubting disease," which means that no matter what logical arguments or reassurances you come across, your brain will bring up more doubts. It WANTS to keep you guessing, afraid, frustrated. So the key is to flip it on its head. Instead of looking desperately for certainty, be OK with uncertainty. Say something like, "OK, I don't know for sure whether or not I made a vow, or whether it's binding. Probably it's not - but I don't know for sure. And as long as I'm in this obsessive 'fog,' I won't know for sure. So for now, I have to just accept the possibility that perhaps I did make that vow, and I will not be able to get married. It's tough, but I'm sure God will help me deal with it." Then, every time your brain brings up this fear, you go back to the same line, the same air of nonchalance. "Yep, my future is probably ruined. Oh well! I'll deal with it somehow!" And move on with your day, doing your normal daily activities instead of giving into the urge to do a compulsion (e.g. research or seek reassurance) like your OCD is begging you to do.
Is this difficult? Yes. So difficult that at times it seems impossible. Is it impossible? No. We always have the choice to ignore OCD, to choose to live with the incredibly uncomfortable feeling of "not knowing" instead of giving into our 'addiction' to seek an unreasonable amount of certainty. It's a very difficult process that requires a lot of repetition (saying no to the OCD over and over again) and perseverance. But - there is a reward. As we do this, bit by bit, ever so gradually, we become able to think clearly once more. To see both sides of the issue; to be able to take a balanced view, instead of the one-sided view that OCD is forcing us to take. We become able to accept, with calmness, a reasonable amount of certainty rather than craving an impossible amount.
I understand how hard this is. I'm still on the tail end of my most recent obsession, one that has had me doing very similar things. But I've had to learn to table the issue, to live with the fact that PERHAPS my worst fears are true, and to leave my uncertainty up to God, trusting that He will make my way clear and direct my paths in time. But the more important lesson, in the meantime, is to learn to surrender my need to know RIGHT NOW and to trust His timing and plan. He is good. I believe He will lead you with calmness and clarity, not with fear. For now, your most important task is not to figure out this issue, but to practice surrendering and trusting.
So, the original challenge still stands. You have the power to choose whether or not to give in to OCD. Start small, if you have to. Ignore one fearful thought, refuse one compulsion (even a small one, like the urge to ruminate). Then keep pushing yourself to do more - for example, not allowing yourself to do compulsions for a day, then a week, etc. Even this process is not perfect, but every time you choose to say no to OCD, you take a bit of the power away from it. And eventually, it weakens its grip.
Here is an article that explains the process of dealing with OCD well:
Managing the Haunting Thoughts of Pure O – OCD
Also, I can't remember if I already mentioned it, but the author of that site also has an online FB support group (closed, so your friends can't see that you're in it) for people with OCD/anxiety. I've found that group helpful as well:
Facebook Groups
And of course, I'm here anytime to answer questions or just discuss the process!