I'm sorry, are these men you're talking to married men you have slept with or just the ones you are conversing with on the dating app?
You do know everthing that comes out of their mouths will be a lie, their job is to entice you into thinking your sex is better than the boring stuff at home, obviously this will inflate your ego.
You believe because they have been upfront telling you they are married the truth will duly proceed, not true.
We all know some men will lie, behave badly and cheat at any given opportunity, you are stating this as if you have just discovered Christmas.
The key is not to believe the bullshit that you are special, that you understand the male phyche and you are above the mundane.
Some men use women for sport and to buy into the I'm too cool to be hurt harem is not a strength, not to men, to them it shows your weakness as a woman, willing to service their needs.
But you're going to tell me you need your needs met, then yes fine I agree, find whatever sex you need but not at the expense of someone who has made the brave decision to maintain a monogamous relationship within a world where it's becoming increasingly difficult because men now have a mentality of cheating as a given right.
If you take the shame away from cheating it becomes the norm, I think personally that is not a prefered model, it causes pain, destroys families and creates a blueprint for future generations to copy.
Get your rocks off whenever you want, but personally I wouldn't even give air time to these 'has been men' who have neither the staying or will power to realise what they have at home.
Shut them down and give credence to the honest available men who may have a little more integrity, FWB or not.
Respect yourself and respect other women. Simple