How do I tell my family that I'm in love with my stepson?!?

I'm 58 and I've been married for 10 years to a great man, but have recently fell in love with his son who has been giving me lovin when his father is on business .. he's brought new energy into my life and made me feel like a woman again .. I've started wearing short shorts mini skorts and fishnets again. How do I tell my husband that I'm leaving him for his son and we're getting married?