Teeth Grinding

I'm just wondering if any of you do this and what made it better? I sometimes have jaw pain and teeth pain and I thought it was because of my molars that have been growing in, but two of them are already fully grown and I still occasionally have pain. Well a few nights ago I woke up my SO from HIS SLEEP because of how loud I was grinding my teeth (I never knew I did this, apparently I do it when I'm sleeping). I'm sure lately I've been doing it more frequently because lately my teeth just feel sensitive and I have discomfort. I'm thinking of getting a mouth guard, do you guys know of any good ones that I can buy without going to the dentist for one and spending more than I need to 😐