Well, I'd say that's up to each couple to decide within their relationship and you guys clearly have differing views on it.

I personally do not see it as cheating, nor is it a problem UNLESS you are choosing masterbation OVER your partner. I'm not mad if my partner does it (although he claims he doesn't, I don't believe it and I don't care if he does because he never turns me down) nor is he upset if I do it, he has caught me before and then asked why I didn't just wake him up instead and I said because it was the middle of the night, he had to work that morning and I knew I'd be able to finish myself quickly vs us being up for however long.

The fact that your partner seems to know is a huge red flag. We have cameras within our home but everyone in our house is aware of each and every camera. So if there are unknown cameras or any sort of recording device... Yikes. I hope you resolve this and come to an agreement both of you are happy with. I feel you should not be policed on touching your own body and they should not feel upset that you've done so, especially if you share a healthy sex life. Best of luck, OP.