Is it too late to stop this potential affair?

I have been married for 12 years, have two children from a previous marriage aged 21 and 18 years of age and am very very confused. My marriage is good, we still get along so well, make love at least twice a week, but unfortunately it seems that 5 min is all it goes for. I am so frustrated. My husband realizes this but no matter what we try I am the one left wanting at the end. Even with heaps of foreplay the end result is the same. I am 38 years of age my husband 48. Recently I have joined a social group within our town so that I can get out once a week and have a laugh and catch up with friends..We both work 5 days a week, so this is my time and I really enjoy it. But recently I have been having feelings for a guy within this group. He is young 26 and a totally different personality to my husband. He makes me laugh and also the attention I get from him really does make me feel good. Before I go any further I need to point out that during my 12 year marriage my husband and I have tried 3somes, swinging etc to give our love life a buzz, but I have never done anything without his knowledge, so I now have this 26 year old who has all but said come to bed with me and 80 percent of me is yelling yes but 20 percent is saying no. I just want to feel alive again even for a moment. I get text messages from him that send me insane with want. Has it gone to far already to stop? and really I don’t know if I want it to.