I know it is wrong to cheat on your mate, but......?

I am married to a wonderful man and have 2 kids together.I am middle aged, going thru pre-menopause and it seems mid life crisis. I am dissatisfied at home or other wise i would not consider this. I have recently been in contact w/ an old high school boyfriend.we always flirted together at school .we kissed a couple of times but that was it. I have even to today always wanted to be with him just once in my life. if it could and would be kept a secret,not to mess up my home life, would it be ok to have my one time w/ this guy and no one will ever know but us 2. this maybe my only time to do this as he is moving far away in a few months and i may never see him again. what is your advice for a confused, always been a faithful woman....