Honey, If you have a good man and have a (basically) happy marriage, be THANKFUL... you do NOT want to be single and out in the dating scene at age 40... TRUST ME on that...
The grass always looks greener on the other side.
I do understand where you're coming from though... I've been married & divorced, so I've had it both ways. Try to do some things to shake up your routine; every marriage has its ups and downs; you just have to weather the storms.
Think back on when you first met and how you felt about your hubby in the beginning; that always helps to rekindle the spark and put things into the proper perspective.
Also, go out with your friends (married and single) and talk to them about how you're feeling. It helps to speak with women who are going through the same issues you are, and it will also help to hear from the other side. I'm willing to bet that being single again will not seem quite so appealing.
erplexed