Married but fallen for another man?

I've been with my husband for 17 years & have children. I have known another man for 5 years, also married with children. We've always had a jokey, flirtatious banter going on between us. Last year he asked for my mobile number which i gave him (big mistake!) Over several months of texting the texts became more ual in nature. We met alone a number of times & got fairly intimate on one occasion. We then decided to stop seeing each other for the sake of our marriages &our children. However it is practically impossible not to see each other because of how we know each other & any change to this would raise questions. He told me he loved me while this was going on & since we have split up i realise i am in love with him. I have tried to maintain my marriage but my heart is elsewhere. Do I tell this other man how i feel? How do I know if it is love or whether it's just infatuation? Practical comments please not criticism i know it was wrong just didn't see what texting would lead to