ONce a cheater always a cheater?

Hey everyone I got a problem n need major advice. I've been together with my partner for 3 years now the shits been rocky but we still together. The entire time we've been together I havnt cheated. Im my past relationships I have. But with this one I thought it was diffrenet. Well for the past 2 months I've been itchin to cheat. Theres this fine ass woman a work who i've been trying to avoid cause I know if I open my mouth its goin to start a world of problems for me.  I even told my partner about the girl at work she's encouraged me to "step out" cause maybe thats what i need. My head is spinning because the sex between me n my wife is crazy. But right now its like I want this other chick n cant get her off my mind. To a point im upset with my wife cause when i bring the chick up or she does she acts like she dont care, or she encourages me to talk to the girl. In the back of my head im like wtf I dnt want to step out on my wife. I know if I step out it will cause more pob. with my relationship n not just that 90 percent of the time when i've cheated caused a stalker which i really dont need. WTF am I to do?