Okay, 1 ... stop looking outside your marriage.

2, you both and you in particular need to sit down and be very honest. You need to give the marriage a fighting chance (see 1) and work hard. After you've exhausted all options and done everything humanly possible (counseling, couple's exercises and such) then if you are honest with yourself and wife and you still won't be happy, then it's time to consider parting ways.

But, don't look outside your marriage, be honest with yourself and your wife, work hard and if nothing works, then consider for the happiness of each other moving on. Don't do the opposite by messing around outside your marriage and not being honest with yourself and her.