You're probably one of the most gullible people I've ever come across on here. If you think that your man will never cheat. Nobody's writing the male sex off. Most women think most men are OK. Sometimes men get on our nerves, sometimes they make us laugh, sometimes they piss us off, sometimes they are kind and thoughtful. But men, (the vast, vast majority of men,) will eventually cheat in a relationship. What percentage??? No idea, but it is the majority for sure.
I'd been with my husband for 20 years and married for 15 and had two young kids. It's a long story, but basically I discovered he was having an affair with a woman at work, when a message popped up on our JOINT computer from her. I had suspected for a few months, as this woman at work was super friendly with him, always texting him, and ringing him on our landline keeping him chatting at dinner time, and he started to come home an hour after he had finished work - it was 10 minutes bike ride! 
But they were just 'mates.'
I complained profusely one night and said I was sick of her contact. Then it went radio silence. He was then in touch behind my back and met her behind my back a few times (pretended he was with mates or at work - I discovered this later.) The message coming through, I won't go into it, but it TOLD me they had been shagging. I reckon she wanted me to know. She knew we shared a computer.
He's always been, ever since I've met him, really friendly with other women because 'I can't help it if I get on better with women, can I?' He has been friends with only a small number of men. I have never understood why. He gets on OK with them, but has always seemed to prefer to be friends with women, and has always had female work colleagues as friends. He has had a few male friends, especially when he was a lot younger - 20s and 30s, but since about his late 30s, they have all been female. (He is nearly 60 now.)
Most women have actually been OK with him wanting to be mates, and have been - and stayed just that. But he has known several women in the past, (colleagues and acquaintances,) who have got the wrong idea and have really been annoyed and pissed off when they see me - because they realised he is married. (Obviously never told them.) They act like I'm in the way, and ignore me, acting as if I am not there, and flirting around him. But as I say, 20 years went by. Never any sign of him cheating all that time.
Although he did used to go out on the odd night out with men from work, (six or seven of them,) and he would come back and tell me tales about all of them, how they tried it on with other women, and got off with other women and he was scolding them as he went home happily to his wife. After I caught him out having an affair after 20 years of marriage, I thought 'you were one of these men, weren't you? You said THEY were doing it when you were doing it.' He used to tell me tales about how women used to chat him up, and he pushed them away. But it was a big fat lie. Fuck knows how many women he chatted up. May have been one, may have been none, may have been twenty.
Anyway, that was 20 years ago. I had an affair for 3 months a year after it. With a man I met in a bar when I was on a night out with a friend. Slept with him 5 or 6 times and then ended it. Would I have shagged another man if DH hadn't shagged another woman? Probably not. I thought - rightly or wrongly - 'well it's good enough for him to fuck other women, so...' I know... a stupid way to think but I wasn't in a good place then.
But anyway. We're OK now. Have been OK since about a year after MY fling.
But even now - married for over 35 years and in our late 50s, there's still a little tiny part of me that worries a little bit when he's trying to help a woman at work who needs his help with something, and she is contacting him by text or whatsapping him, or ringing him, and he is reassuring her about something, and chatting.
One woman (at his workplace) was pouring her heart out to him about 3 and a half years ago, about her broken marriage. THAT jarred me, because it was when a woman did this 20 years ago, that he ended up fucking her. This time though, he kept this woman at arms length, and told her after she had kept him talking 3 or 4 times, that he felt uncomfortable chatting to her about her personal life. She left soon after.
It also jars me when he is a bit chummy with single female neighbours, and (for example) offers to mow her lawn... It is still in the back of my mind that even at nearly 60, he could still cheat. I also never understand why he doesn't ever offer to mow the lawn for single MALE neighbours. These things run through my mind. (These women always decline the mowing of their lawn btw. Don't want to be beholden probably.)
(He doesn't do this often, offer to do stuff for female single neighbours, and hasn't for several years, but he does now and again...)
He also is quite old now.. like me. Nearly 60 and hasn't 'got it' anymore. He has tried to make friends with women a few times over the last 2 or 3 years, (at work,) and they are not interested. Doesn't help that that they're pretty much all a generation younger or more.
Why am I with him? When I've got this slight doubt in my mind? Because for the most part, probably 90 to 95% of the time, everything is absolutely fine and our marriage is good, and we are good friends, and I do love him and we have children together - and future grandchildren possibly, and as far as I know, he hasn't cheated again, and probably won't again. And I'm not going to give up a perfectly decent marriage, where I am very financially comfortable and happy, because there is a vanishingly small chance he might cheat again.
I really don't think he will. But yeah, anybody who thinks their husband will never, ever cheat, (not my Nigel,) is incredibly deluded. Most men will take it if it's offered on a plate, as at the end of the day, they think there is something out there that is better than their wife. After a while, they realise there isn't and that's why men usually stay with their wives. Also, it's a lot easier on them to stay, than leave. And even the ones who DO leave, end up finding everything is the same as it was with their wife, but they have destroyed their wife's heart, and confidence, and upset their childrens lives, and the lives of both families.
What it boils down to is many men are selfish and entitled. Thank God most women are NOT, otherwise we'd all be fucked.