Is my Invisalign killing my tooth? Or weakening the enamel? My front tooth is changing colour to a grey/clear colour.

Hi!Yes, a grey tooth is a sign that the nerve may have died and sensitivity is also not a good sign.  Please see your dentist and a endodontist to confirm the need for root canal.  Even though it is rare, tooth movement can cause the need for a root canal.  There are also other causes for a tooth just to die.  It is hard to tell.  It's best to know and take care of the situation now.  Please call your dentist today and he/she can help you.