Thinking back, there have been times where he's pushed boundaries sexually - but he's always so loving about it that I feel like I'm denying him something that will make him happy. Looking back I realise this sounds pathetic.
It doesn’t sound pathetic. You love and trust him and believe he cares about you so you give him the benefit of the doubt - the person who exploits that trust is the pathetic one. You have done nothing wrong.
I have been exactly in this situation and it’s like being the frog in the boiling pot. It’s so gradual that you don’t realise - hell, I even managed to convince myself that these were my preferences too, since it was easier to believe that than to be believe the truth (that someone I loved was openly and obviously sexually abusing me on a daily basis while saying they loved me). Eventually things escalated to a terrifying point and I left after getting badly injured. I still felt responsible as I hadn’t told him to stop.
It’s only recently, now that I’m in a much better place, that I realise how much it traumatised me and that it’s actually made me frightened of sex. Even in a loving relationship, I’ve found that I don’t say stop if I want things to stop because I’m scared of being on the receiving end of anger and emotional abuse. I literally realised recently that I’m afraid every time I have sex because of what he did, even when I know I’m safe.
Sadly I expect the more you analyse the trajectory of your sex life, the more concerns you will find - it’s really a shock to find you’ve been abused all that time and didn’t see it.
Please be kind to yourself. You are not pathetic. He’s taken advantage of your love and trust. A good person does not treat someone they love this way.
And please, starting right now, rethink this belief. You are allowed to “deny him” sex acts that make you uncomfortable and that is not a hardship for him. That’s a relationship where both people have boundaries. If you wanted to do something very extreme sexually that he would find humiliating, degrading or painful, would you expect him to go along with it to make you happy? Could you enjoy yourself and have an orgasm knowing that he disliked what you were doing? I bet you could not, but he can get off knowing that he has pushed at your boundaries - that is not respect or love. It is abuse.
Coupled with knowing full well that you would not consent to these images, hence doing it behind your back, you are starting to realise that he is not demonstrating respect and love for you. And that’s heartbreaking when you thought you had a great relationship.
You need to make sure that you physically have hold of his devices and insist on full access, to anything you haven’t been able to check, before you bring this up. You need to be clear that he must tell you the full story because otherwise you’ll be going to the police so they can investigate, and if you ever discover anything he hasn’t told you, you’ll be saving the evidence so you can go to the police then. Insist that he tells you every single place they are posted online so you can try to get them removed, as if you ever find any he hasn’t told you about you’ll go to the police.
You may decide to go to the police anyway, but the threat of doing so at the slightest hint of a lie might be enough to get the full story.
Make sure you get evidence (screenshots, photos of your phone) before anything is deleted. Make sure that anything deleted is also deleted from the cloud - sadly very possible that he has back ups somewhere but again, threaten the police if anything that comes out later. Tell him you’ll report him to his employer, tell his family, whatever you need to say. Make him feel some of the shame and humiliation you’re feeling right now.
You don’t need to decide what you’re going to do about it now. You do need to address it as soon as possible though, to prevent this happening any further / any more sharing. Obviously do not have sex with him, or be naked around him. Make sure there are no cameras in your bathroom or bedroom (i would be getting changed in a different room for now to be honest - you’d be amazed at the tiny places hidden cameras can be).
Have you tried doing a reverse image search yet if you have any of the photos? I know that could be distressing but it might give you some info.
Please talk to a friend you trust. If you were my friend I would want to support you through this.
You’re welcome to send me a message if I can help at all. I’m so sorry this is happening.