I don’t know what to say, OP.
You are 26, have never worked and am not sure if you are married to the father of your children. It’s quite vulnerable position to be in and even if you didn’t have all the above issues - I’d say you need to figure some plan. I presume your kids aren’t babies anymore - so you can go and train for some profession.
As to the rest.... I am looking at it from a different phase of life. I am almost twice your age and it seems to me that what you are going through is quite common in relationships that started very early. You were a teenager and he - barely an adult. Normally these relationships don’t survive and for a good reason. People grow up and change a lot. And usually people play around and explore before settling down. You two have skipped that phase. It often catches up with people, around your age and length of relationship....
I think it’s extremely difficult, if not impossible - to go through life with just one partner. Never wondering what it feels like to be with others.
However, it didn’t go that far, it was only a kiss... And who knows what really happened. Was alcohol involved, for eg.
I will get a lot of flak for it - but in reality - most people wouldn’t end a relationship over a kiss - not where there is a long history, and children involved.
People make mistakes. He made one. Have you tried to figure out what lead to it and try to see if you can move from it together?
You had quite an extreme reaction and you seem to be only getting worse - have you tried speaking to a professional?
And have you thought about couples counselling?
When people are younger - you tend to see things as extremely black/white. Which comes through very strongly in your post. Life doesn’t work this way, not over a long term.