Thoughts are random fleeing "things" flying in your mind. Desires is actually something you want to do. Ocd mixes them both.
A desire is something that when you think of it you like it and would like to do that thing. A thought is just something completely random that is just in your brain and sometimes these thoughts can be disturbing and your ocd decides to latch onto it and make it something it’s not to a point where you might think the thought it a desire when it’s not .
Can you resist answering that? Can you imagine that ocd is posing that question to you and reply by saying “nice try ocd”?