ive been told i have low results of asbestos in my ceiling
Some ceiling tiles contain asbestos; some don't.  If you want to be sure then you can have it tested.  If the tests come back negative, then you can stop worrying!  If you don't want to do a test, then I would do something about it right away, just in case.

Asbestos can cause problems when inhaled, but not when touched.  If you've had pieces falling off of the ceiling, you may have fibers floating in the air.  

The particles are small and light enough that they never really settle as dust.  HEPA-rated filters will remove asbestos from the air, but only if they are attached to a matching HEPA vacuum.  If you put an after-market HEPA filter on your shop vac there are any number of ways for the asbestos to get around the filter.

Keep in mind that asbestos is a politically hot topic.  Some people believe that a single fiber will lead to inevitable cancer. Others believe that you have to breath fibers for years and then maybe something bad will happen later in life. The truth must be somewhere in between: Asbestos is a naturally occuring mineral, and is always present (in low levels) in the environment.

Either way, asbestos is a controlled "hazardous substance".  If you get a positive result on an asbestos test then what I'm about to suggest may not be allowed (especially step 3). You can Google "asbestos remediation" for a lot of information.

I assume you don't want to buy a new vac.  Then there are three things that I'd do:


Stop adding possible asbestos to the air. You need to repair (or stabilize) the damage in the ceiling. This can be difficult to do without releasing more asbestos :)  One common way is to cover the asbestos-containing material with sprayed-on paint.  But this isn't appropriate if there is already damage.
Be wary while cleaning up the fallen material. You can mix a small amount of dish soap into water and spray it onto the material. This traps the fibers so they don't get released while you scoop up the material. Keep it wet when cleaning it up and then tie the garbage bag closed.  If the material is known to contain asbestos then it is generally illegal to throw it into your residential garbage container.
Ventilate the room. Get a lot of air flowing through the room through an outside window.  Don't blow the air into the rest of your house. Any fibers will quickly disperse in the atmosphere.  Again, this isn't generally allowed if the tests have come back positive.