After a while on these threads the measured, thoughtful few become drowned out by the angry, knee-jerk many.
Of course good people have affairs. If I'd been cheated on I am sure that I would be permanently unwilling to concede that.
If I had been in the dark about my husband's affair I would insist that any cheat I knew told their spouse because I am sure there is nothing more humiliating than thinking you are the one who doesn't know.
For some of those who advise you that you must tell your husband, the motivation is to see you get your just desserts, so you don't 'get away with it'. It is not necessarily based on any principle.
You've done something stupid; you will probably do it again unless you process why you had the affair and recommit yourself in your mind to your husband. You've humiliated him whether he knows it or not.
This doesn't necessarily make you a bad person, that's a meaningless expression anyway. You did do some bad deeds.
I supsect that coming on here won't do your self esteem much good. I am not sure why you are here. If you want advice as to how you can get a book delivered without anyone finding out you can get that anywhere.
I think you are either here because you are a bit immature and you like rubbing women whose partners have cheated's noses in it (because this is your displaced humiliation of OM's wife) or because you want to masochistically attract some abuse.