[freeflight]

When the question is "What do you do on the weekend", then, of course, people with partners will most likely respond with something involving their partners.

How does that imply a problem with the OP, except his inability to magically know the relationship status of his coworkers? Which would be the only ability allowing him to evade such answers to a rather casual question.

Maybe he's new in town and looking for places to go to during the weekend? Is the weekend question really that inappropriate in such a context?

[DanBC]

OP has interpreted this as not being g a problem. I'm looking out that if many people felt the need to drop the "I'm not interested in you, and I have a partner so back off" line then maybe there was a problem.

[freeflight]

That's the thing with these kinds of situations, whatever the OP original intentions had been, they don't matter anymore as soon as the other party thinks he/she is being "hit on" and feels offended about it.

If the other party is actively looking to be offended, then there's literally nothing one can say/do to make it not worse, just walk out of the situation in silence and take a break.