Unfaithful mind

First off I just want to state that I don't want any judgement what so ever. Here lately, and it has been getting worse, I've been wanting to be unfaithful and cheat with another man. I love my boyfriend more than anything and want us to be a happy family with our 3 year old son. But recently I've had guys from my past on my mind and thinking about the things that I miss with them. I know that there is no perfect relationship and that you have to compromise. Maybe I'm just weak because I know it might be ok to just think about things and go on with your life without ever acting out those thoughts but I just think about them more and more and find ways to act on them without getting caught and ways to not make me feel so guilty. Before my current boyfriend and I got together he tried to get me to go out with his best friend Allen who I turned down because I had feeling for him not his friend, not knowing that we would ever be this serious and be together this long. And now after all the bad that has happened in our relationship and we have moved back to my hometown(where we met) and he's hanging out with Allen again. I'm starting to regret that choice, not that I would see myself still being with Allen now but I think deep down that I just want something better and don't think that I deserve it. I have a lot of personal problems and don't want to take the chance that someone other than my boyfriend would accept. Which I know that out of all the people in the world I know he's not the one but I would have to take a lot of chance and getting hurt before I would find them so I would never choose to put myself through that. So instead of breaking it off with Nick(my boyfriend/child's father) I stay with him and think about cheating to fill that void and maybe just deal with wanting more or better. The guy(Will) I cheated on Nick the first time 4 years ago has started talking to me again and trying to convince me to cheat again but I told him no because it's wrong and I wouldn't feel right but really I only said that because I've had a child since then and since we moved back to my hometown and I quit working 4 months ago I've gained a little weight and I'm self conscious about my body that I would be to nervous to be naked around him. But I also don't think I would be ok with just having sex with Will and that be it, I think I would want more not necessarily with him but with someone else cuz I know all he would want is sex and nothing more and I'm not saying I want him to want to be with me, that was out the door a long time ago. We've never done anything other than just have sex and leave so that's our only relationship. But if I were to cheat then I would want it to be worth it and not just be meaningless sex. I want passion and excitement, something different! I'd want to at least talk and have some kind of emotional relationship but to never get feelings involved and someone to want more. But maybe I'm too weak and can't be ok with what I already have. I know it's wrong and friends will say I shouldn't do it but is there ever a time where it is ok to have cheating in a relationship just so that the happiness can continue? Couples have open marriages to stay happy but both partners know and it is agreed but maybe sometimes it's better to not know.