Help with a call that keeps bothering me?

[Benzbmr]

I play Division III basketball in Massachusetts and am pretty aggressive when going after shots around the basket. I've had 6 or 7 occassions this year where I had a fastbreak 2 on 1 against me. The player at the top of the key slows down with a player on his right side. I stop at about the dotted line waiting for the pass to the player at his right/my left. When the pass is made a drop to the basket and leap for the glass. On all these occassions I've caught the ball against the glass and been called for 3 fouls and had 4 called clean. My problem is that I've had 2 of the 4 clean calls where the guy fell to the ground after my block, apparently from my contact with him. Then I've had 2 called where I went up, blocked the shot, came down with the ball in my hands and made minimal contact with the shooter but yet it was called a foul. Is there any specific thing that you look for when a block is attempted during a fast break? Is it about timing? I'm just trying to figure out how I can keep from picking up these fouls while still contesting the shot. Also, how can I approach the official after one of these foul calls without him taking it the wrong way? Any help is much appreciated.