Please create another email address that he doesn't know about. You can also create a new FB page too, just use the new email address and limit your friends on it to people you trust to not go tell him. Then you can use a different device or log in and out each time you go on them.
Then use the old email address for online purposes and the new one for strictly private conversations. Same with the FB new account. Only go on it when you are alone and can see what your friends are up to. You can block him too, so that he can never see you are anything you do.
As your information wanes on the old accounts hopefully he'll lose interest. He's getting stimulated by your life. This needs to stop. One thing though. If he catches you with the new stuff you'll be in trouble so you do need to decide what you're going to do at that point.
I don't care if my husband sees my general stuff. I do have a friend that I like to rant and get all my angry comments out with. She is very supportive and I listen when she's got to have someone to talk to.
I have a different email address for her specifically and she has one specifically for this too. We aren't doing anything wrong, if we could talk for hours on the phone we'd do that but gee, we both have school age children and we have too many things going on to take that sort of time. So we email back and forth, like it was a conversation.
I use a gmail address for my personal email that pretty much anyone who sits in my chair and looks at chrome can see and open and read all they want.
When I made my alternate email accounts I went with a totally different provider that I have to go to, there is no link on my computer or phone at all. I do NOT stay signed in or have quick access to it.
If it was yahoo I'd have to go to yahoo.com then log in with a user ID and password. When I was ready to leave that email account I'd choose to delete all messages and sign out. Then close it down. SO there would be no trail to it. I'd also clear my search history so no one could see where I'd been.
But again, my husband can sit down and go on my FB and gmail account anytime he wants because I don't care if he reads it or not. There is no invasion of my privacy because I've never really cared. I do care if he sees my angry words and crying out in pain over his illnesses and mental illness issues and more. That's not his business because sometimes we all have to rant, to lower our stress levels. We lash out, say things we think but squash because it's not how we truly feel. Those are the things I want to keep private.