Could it have been mate sooner?

This is my first ever checkmate like this, it’s like a reverse bishop checkmate lol. But the question is; could it have came sooner? Did I waste valuable moves by trying to trap his queen? It seems to be after 15. O-O for black, it’s a force checkmate? But by messing around with his queen I actually let him get into a defendable position (that he just blundered)

That's never a forced mating net... Just moving the bishop after move 15 saves it.

16 bb8 is probably better

Moving the LSB with a discovered defense is the best option for black, preventing mate but just in a bad position

You could have moved the bishop back earlier