Hi tigerallenyim,
I used to get a 'shroomed tip myself and also a bunch of unexpected miscues because of it. I say 'unexpected', because I hardly use any more than 3/4 to 1 tip of English.
It's mainly due to my (old) grinding method of chalking: applying chalk using too much force, scraping the chalk from the cuetip's top to bottom. Unknowingly I'd remove the chalk off the edges of the cuetip which is essential for gripping the cueball when using English.
Also, I believe the edges of a mushroomtip can't hold chalk as well as a non-shroomed tip.
A cue-repairman I know, who himself plays with a Sniper tip (like I do), told me that shrooming is usually related to the way how you chalk the cuetip. Makes sense to me, since I used to grind the chalk from the tip's top to the bottom. If you do this a lot, you will flatten the cuetip and make it shroom over time.
Chalk is basically a piece of stone and grinds the cuetip. Since a cuetip is softer than stone, something's gotta give. That same cue-repair guy told me that a (Sniper) cuetip is so strong, it only wears out because of the chalking. You could go on playing with one cuetip for a long long time -I'm talking YEARS- if you didn't have to chalk.
The same cue-repair guy told me to 'wipe' on the chalk instead of forcing the chalk onto the tip. Now I hold the cube of chalk in my left hand, hold the cue pretty much horizontally, and put the cuetip in the cube and rotate the cue - without really pushing the cue into the chalk. Result: my ferrule is much cleaner, I have less miscues and the cuetip stays in shape.
My advice, if your cuetip is pretty flat/worn out, I'd replace it and start chalking without using (excessive) force. If you already chalk without forcing the chalk onto the tip, then forget I ever posted

.
Also, chalk with your own cube of chalk. Your cube shouldn't have a deep 'hole' in it. It should have a hole similar to the hole it has (maybe slightly deeper), when you get one fresh out of the box. When the hole gets too deep, you might damage your ferrule when chalking.
In order to avoid this, once my cube gets worn out too much, I scrape the chalk on a pavement, getting rid of the edges and making the hole less deep again. This will ensure you will be able to wipe the chalk on the cuetip with ease.
I hope this helps.