How do i get my husband to stop cheating?

been married 6 years, together 15, 5 kids, all his, i am 15 years his junior,and in my opinion still very attractive. so why the cheating? i'm not a mega *****, nor am i a slob or lazy, i don't overspend or gamble, i never cheated and i'm not a flirt. he does see other men hit on me from time to time, but i turn them down gracefully and move on. i sometimes think it stems from insecurity, but i'm not the type of woman who accepts infidelity and makes excuses, i'm just honestly giving it one more shot before i move on, i feel my family is worth fighting for. so does anyone have any solutions for stopping a cheater?