Candyfloss99
This is why you should leave when you want to and not "stay for the children". All it ever does is cause resentment
Some of us really can't 'leave for the children' when we want to, and need to find a way to solve the feelings that come from that, rather than getting the same tired old response to this issue on mn.
So I really do feel for you OP. My situation is similar, although not exactly the same. But some of the responses are so harsh - it's as if people can't imagine any other kind of life beyond their own 'ideal world'. 
But what about when a marriage is dead in the water (just because it's a mismatch, not for anything awful like DV) and marriage partner A meets another person and falls in love, and confesses it to marriage partner B while DC are still at primary school (because marriage partner A doesn't want to deceive anyone) but marriage partner B still wants marriage partner A to stay 'for the children' while the DC grow up, regardless of the affair, even while knowing that the affair will continue (and has - in the present day - now continued for nearly 8 years). Meanwhile, the DC have grown up to teenagers.In mumsnet world this never seems to happen, or be an option.
But - in the middle of all of this - marriage partner A has no job, no independent means of earning, and no independent access to housing (not in the UK - not everywhere in the world has the UK options...) or access to any state financial support, so has to rely on what marriage partner B earns/shares (and has willingly continued to do so because marriage partner B still doesn't want to 'split up', affair or no affair on their partner's behalf).
So there's no financial abuse, just an inability for marriage partner A to earn enough money in their own right to house themselves where they live, but can't leave because of the DC.
So, OP, not everything is as simple as mumsnet world makes out so please remember that you are a person who can be happy too, no matter what that takes. There are huge degrees of grey between 'happily married' and 'marriage not working = divorce'. And some people really do need advice of how to 'sell' this odd kind of arrangement to their teenage children, knowing that it's never going to change, knowing that marriage partner A will always have to stay married to marriage partner B because financially there is no way around that if they want to stay in the same country as their DC, and yet marriage partner B condones marriage partner A having 'someone special in their life' and wants the children to understand that (both boys, if that makes any difference).
I'm not sure any of that makes much sense to most pp on mn, but it's my life nonetheless, and I really do think the OP needs to go and grab her chance of happiness because there are worse things that happen at sea, and DC can (and should be able to) understand that life isn't always simple.
Sorry, that's long. I NC for this, so will not use this name again. Just wanted the OP to know someone is on her side.