This is actually a really common situation, and you are obviously devoted to your family. Think about it as if a friend asked you the same question. Having a big wonderful family is very self-sacrificing, time-consuming and stressful. When you were dating your ex life was probably a lot more simple and the nostalga that you feel may just be a mental escape to a time that was simpler. Everyone does this and it's totally normal.
Where it starts to go too far is when as you said you tell your ex that you feel this way. There is no closure there - it's the opposite. You are opening dangerous doors that can put your wonderful husband and family at risk, and from the sound of your message that is out of the question.
If you do decide to contact him and you can keep a platonic relationship, then it's perfectly ok to talk to him on myspace or email back and forth, but you should also let your husband know for a few reasons.
1) Respect - When you are in a healthy relationship, you put yourself in the other person's shoes and see what you would want him to do if the situation was reversed. It's not that you have to have him approve who you have contact with, but it's just respect so he can let you know his feelings as well.
2) Trust - If he finds out that you are contacting this ex behind his back, he may feel that you are doing something dishonest and losing trust is the first step of many in a downward spiral toward many other relationship issues.
3) Accountability - If you tell your husband you are more likely to consider him in your decisions with the ex as it would be easier for him to find out if there is any foul play if he knows you are talking to him.
Affairs are a slippery slope that start at the crossroads where you find yourself. Remember that you are grieving the carelessness that came with that time and since your ex was there, you are confusing that for your feelings for him. Life may be more complicated now, but isn't it more fulfilling? Would you go back to being that age again and have to go through everything you've been through over again?
Good luck!








