should I

I've been with my fiancee 17 yrs. I have 3 kids with him and he raised my oldest daughter as his own. we are suppose to be getting married next year for our 18th year anniversary. but I have been having feeling for someone else. I've never met this person face to face. but I enjoy talking to him and he makes me feel good about myself. He knows im married I tell everyone I'm married. but he said he is fine with just being a fuck and it could be our little secret. He very tempting he makes me excited again. being with the same man so long it gets to be routine, but I don't want to lose my family. and I love my husband. What should I do? I havent felt like this in a long time and never thought about cheating on my partner until this guy showed up. please help

okay ladies thank you for ur input I do love my husband and I'm going to delete this man. and work on my relationship. thanks again