Life, alas, does become mundane - it takes effort to make it less so - and you can't passively rely on another person to keep the fires burning through their personality alone.
@TossaCointoYerWitcha I know just what you mean. In your situation, your role by definition cut you out of the running for being the passionate excitement. You were the safe dependable part of the furniture ... (in her eyes, her perspective).
It takes active work on one's mindset to find that familiarity and domestic closeness with a partner sexy, and sustainably so. It is more than possible. You just have to shift your thinking slightly. To make a quantum difference. To find things like the power between you to make new life super sexy. To build layer upon layer of love with each new day of experience together. To feel, as a woman, that it is more sexy to have sex a thousand times with one other, than for a thousand men to want you.
(oh and @TossaCointoYerWitcha - I don't subscribe to the golden height model - I lay awake next to my (5'9'm) partner thinking a lot about that too - it's the kind of thing teenage girls value, and linked to signs of sexual maturity in adolescent males - once you're all past 20, it should stop mattering in the same way). (Especially as your sexual maturity has clearly been proven ...)
@TossaCointoYerWitcha is right, OP, that this takes work and a definite decision. His wife wasn't there, and nor, it seems, are you.
You are questioning the very foundation of your relationship. Did you marry him and build this life just because you wanted the security and status and a few other perks like a house and kids? - you ask yourself.
Do you actually fancy your husband? How much older is he, that you say one day you definitely will find the age gap a problem?
Don't beat yourself up about the decision process (or non-decision process) that got you with him. But I think do beat yourself up a bit now about your urge to need to be 'wanted' (aka wanked over ...?). You have more than just yourself now in the boat. You have your children. Life is very easy and calm and secure now - even if that doesn't feel like what you want, it is what they need. It is very good for them.
Either work on loving what you have, or be duplicitous and feed your desires with these covert conversations and flirtations, but whatever you do - consider growing up. You have it very good. It could be very bad, for you and the children (and the poor older DH).
Or leave, break up the home, distress and confuse the kids, in pursuit of a satisfaction you may never find within a secure domestic long term relationship.
Face up to this: you lost the ex you think was best. You vacillated on the major decision of who to be with. It was understandable to question your choice - it's a big decision - but it was not acceptable to run from one to another, and the result was you lost the option.
Is the dilemma now whether you should contact the best ex?