How is it different? It's only different because it's NOW and the other crushes were then. You only believe it's different because you have some need to fix her, some want to be needed in some way that your wife isn't currently providing for you because she has taken over the role of the dominate partner (mother) to your subservient one (son). You can get back the emotional and sexual connection you once had with your wife if you work on this together or with the help of a marriage councelor/personal therapist if you can't figure out how to get the spark back you once enjoyed together.
I suspect your wife has taken the role of your mother because you have taken on the role of her son and she does most of the running of things, yes/no?
It's no wonder you've lost sexual attraction for one another.. afterall, who wants to have sex with their mother/son? Start giving your wife the attention that you've given this other married woman at work, take her (your wife) out on dates and seduce her like you once did when you were trying to first get into her pants. Give her the sensual and emotional attention that you, yourself want and she will more than likely respond to you.
... and no, it won't take years for you to "get over" this fixation you have with Mrs. Co-worker. All you have to do is stop your constant thinking about her by focusing on your wife, keeping busy doing things you like and by stopping the texting and extracurricular contact. You don't even know this woman past the fact of how she is at work, the kind of texted pictures she finds funny O.o and that she is clinically depressed... Hardly fodder for feelings of love.