What a difficult time this must be for you.
It is easy for an outsider to say "get rid of him" but after all you have invested in this marriage it sure isn't that easy.
I agree that your husband was only looking out for himself ( massage parlors, car sex just to name a few). Who knows maybe this is a middle age thing? He should have bought himself a boat instead of all this foolishnes but it is time for you to look out for yourself. Go to the dr.'s, perhaps even try counselling and continue being a good mother to your children. He may thing his actions are wonderful but in the end you will come out ahead.
I hope this helps and I wish you the best.
sing like no one's listening
dance like no one's watching