Want to reiterate along with Wooba and Yail-- you are not a fool. Far from it. You lived your life with the expectations we all have and trusted your H to be there through thick and thin because you're supposed to be able to trust that person to be there for you and not to change their mind or whatever. To me, there is no purpose in seconding guess decisions you made in the past, or wishing you had noticed something sooner or done something differently-- you did the best you could with the tools you had at the time. Might you do things differently now or in the future? Of course-- and that is the best part of all of this, we are constantly learning and given opportunities to do better, learn from the hardest things and apply that to our future relationships.
A couple of questions or suggestions for you... can you resist the instagram searches? does it serve you? I mean, if it does-- if knowing he's dating someone else, and knowing who she is etc is helpful for you, then by all means. If not, if it is just a way for you to go in circles, then maybe try to resist. Another thought.. I have read about some of the fabulous vacations you've been on since all this (honestly, an inspiration for me) and am wondering if you can start planning another, even something quick and inexpensive, just to get a change of scenery and get your mind off of the current situation? Sometimes even the planning can be beneficial.
Hang in there. You are strong.
Me (46) H (42) M:14 T:18, D9 & D11 4/19 - 12/19: series of escalating BDs 9/20 - present: R and piecing