The relief when you find out ie 'get proof' of what you already know in some instinct or other, is unbelievable.
I spent about 12-18 months in that stage. The infidelity had gone on for 5 and a half years, it turned out.
I kept doing that things others have mentioned of thinking it was just me, eg when i found something possibly suspect and he denied it. Of course, during this time he retreated into work mode and was on his computer all evening and long after I had gone to bed, so the marriage was deteriorating anyway. He blamed me for this, but now admits he just didnt want to take responsibility for anything that didnt suit him.
The blame they deflect gets to you. The suspicion gets to you. The miserable life doing all that they wont in the house gets to you, too. Finally, with me, if became an obsession to catch him and I used to spend hours on the net looking for his typical usernames eg I would put in his ebay username and search on pipl so see where else he came up, as that was a unique name. I looked on dating sites but gave up, because it as like looking for a needle in a haystack.
It definitely lost time in my life over all this. It definitely affected the kids, they said so afterwards. My teenage daughter actually fucked up her GSCEs over it all, acting up and never doing any work and hanging with the wrong crowd, but afterwards she came to me and told me all about how she lad felt . Because i had shown her I was prepared to take action to solve my life issues, she did too.
Also, I became physically ill, and had facial cellulitis on four of five occasions, and lost three healthy teeth through that. There were two spells where I couldnt go for a few days as an inpatient in hospital for IV antibiotics, as he was too selfish to take a day off work or, on one memorable occasion, attend and speak at a conference for which he would not be paid.
When I finally came on mn people tried to explain to me that getting the actual proof wasnt the main issue- i was living in misery anyway. There was no way I could see that at the time, and can understand why you cant either Angel, but I did come to see it eventually, and could have kicked myself.
The main thing is, how happy is your life? Can you see it improving, in terms of your happiness, as things stand?
Because if not, all the work to make that scary jump is just that- work. One step at a time. A trip to a solicitor isnt a commitment to leave. It may well be free, too. It is only a confidential chat to get some information.
Take that step, and see where you are then.
I really feel for you.