There is nothing wrong with feelings. We cannot pick or choose our feelings.
BUT there can most definitely be something wrong with ACTIONS.
Actions and feelings are two different things, and just because we have feelings doesn't mean we have the right to ACT on them.
Now as for this married man. He is off-limits. The more you interact with him, the more addicted you WILL become to him. But you cannot have him. So this is just self-destructive of any happiness you hope to have for yourself. Don't DO that to yourself.
Also understand that just because we are friends doesn't mean we would work out as lovers.
And if we do work out as lovers, that doesn't mean we would work out as partners/spouses.
In fact, it takes at least two years of being romantically/sexually involved with someone before we get our our fantasies about them and start to see the flaws. Until then we cannot see them realistically and cannot accurately grasp if we would even continue to just LIKE them over time.
So you have a crush. Big deal. Enjoy it but don't dwell on it, and understand that a crush is NOT love. Is not LIKE love. Is not lasting (if you actually get together with them). And that psychologists warn us that the more we crush on our fantasies about someone, the worse the actual relationship would turn out to be.
Whole and emotionally-healthy people don't crush.
Never tell this guy about your delusion about him.
Time TO lose him. Do not talk to him, do not even follow him on social media. IF you MUST be around him, never look AT him, not even when talking to him. Otherwise, you slide into out-of-control self-delusion. And you are already perilously close to the edge.