What must I do?

You must do what you think is the right thing, and also if you value your marriage you will not keep secrets from your spouse.

She won't understand. She is very narrow minded about these things.

But she is your wife, so your sex lives are a unit. If you want to leave her and be openly bi, do it. Otherwise, do nothing and respect your marriage.

Helgaleena is correct. You've got to discuss this with her. She may be more receptive than you think. THis may be a case where you might feel more comfortable talking to a therapist first for advice then bringing her in to a safe and comfortable place free of kids and distractions. Best wishes.
As far as this workplace guy...don't touch him. Best way to get caught. Office gossip will get you everytime.

Here is another girl saying.... listen to the girls. You know your wife best, but sometimes wives harbor secret desires as well.. They remain secret desires until the relationship reaches a point where both can feel totally secure and confident that anything and everything can be discussed openly and honestly. (That is where my marriage is...) Sadly.... many never reach that level.

And definitely, stay away from the office guy...dicks aren't the only thing wagging in an office, if you get my drift.... 8-D

Your sexual orientation seems very much like mine, except when I was growing up in rural Arkansas in the 1960's it was very easy to experiment with other boys, while the girls were determined to remain virginal until marriage. I think it is very different now because of the "gay" political movement, most young males are not willing to experiment lest they be labeled as "gay", but on the other hand they are not sexually frustrated because the young females are putting out.
In my case, I grew up on a farm in the Red River bottoms about 6 miles from the nearest small town where we went to school. I was the only young male that I know with intact, uncut genitals, and we all went swimming in the river naked, so everybody knew about it. So it was a matter of curiosity and all the other boys wanted to touch it, look at it, play with it, work the skin back and forth, experiment with it.
In the time and place where I grew up, boys experimented with each other, so it seems strange to me that you could be so inexperienced. But the experimentation mostly stopped at about the age of 16, and the interest was mostly turned toward girls. My wife and I had decided that we would likely eventually marry by the time we were 15, and at about that age, when we were in the 10th grade, she started letting me get her off with my hand. I had always let her look at me naked, play with my dick, whatever she wanted, but she was determined to save it for marriage and it was only after I jacked off for her and let her learn about orgasm that she finally let me get her off with my hand. But I wanted to get her completely naked in a well lit room and spread her legs and really study her anatomy and satisfy all my curiosity, so I was terribly frustrated. It was not until I was 16 and in the 11th grade that I decided that I was willing to go down on her with my mouth, and after I spent some time talking to her about that, and getting her turned on to wanting me to eat her pussy that she finally let me really satisfy my curiosity, except that she would not have full intercourse until I wedding night after we finished high school. Well I thought experimentation with other males was just a part of my development leading up to sex with my wife, and something that I would never go back to. But while my wife loves for me to go down on her, she hates to return the favor. She is not good at cocksucking because she does not like to do it. Meantime I remembered that I had gotten great blowjobs from other young men before I was married and really missed that pleasure. She told me for years that it was fine with her for me to get oral sex from other men, because she did not want to do it herself, but I did not know how to get hooked up with other men since I was not a teenager and did not go skinny dipping in the river anymore, and the world changed so that in redneck places like rural Arkansas there is a big backlash against the "gay" movement, and male with male sexual activity is now something that people are on the lookout for, so that they can condemn it, keep it out of the schools, away from children, etc. So about 18 years ago, I started using my farm truck for hauling cross-country freight in the winters to supplement the farm income and make ends meet. Out on the road, I started being propositioned and having sex with men after not doing anything like that for more than 20 years. My wife knows all about it and she does not consider it cheating as long as it is a man and not another woman. I don't have any love affairs with other men, and I am not capable of having a love affair with a man. It is not cheating on my wife any more than masturbation is cheating on my wife. When I am at home with her, I belong to her, and she can do anything she wants with my body that gives her sexual pleasure. Sometimes I spend two hours licking her clit, and get her off over and over because that is what she really likes.
Well I wrote this whole book of my life to tell you that if your wife does not give good head, it is probably because she does not like to do it, and she might be open to you getting it from a man, if she knows that it would not be a love affair, but just getting off.
If I were you, I would not hook up with the man at work when it is so easy nowadays to hook up on the internet.