I think no one is responding because your relationships sound successful, so who are we to tell you to change what ain't broke?
The only issue seems to be the coworkers, which has nothing to do with the relationships.
I wonder if the interest is sticking around because your story is not consistent? (You mention some people knowing the truth, others not, and still others getting comical untruths). If you have the ability to be out at work, (ie without the threat of losing your job) I would recommend giving that a try. Then everyone gets the same story and they will (eventually, once the novelty wears off) move on to the next "scandal".
If questions get too personal, feel free to remind people that you don't ask for a play by play of their sex/dating lives.