I Have a Front Tooth That I Chipped a While Back (A Little Less Than Half is Gone)? (photo)

Looking at the photo there is obviously a lot of decay under the remaining tooth that you see, possibly below the gums and most likely already into the nerve area (pulp).  Your first order of business is go to your dentist and get an x-ray.  I am absolutely certain that the x-ray will show much more decay than you can imagine!  Then the real question remains, did you wait too long or is the tooth still savable?  If savable you will most likely need a root canal, core buildup, and a full crown restoration.  If not savable, extraction and either replacement with implant or fixed bridge.  Since your dentist advised the root canal two years ago, so much time and decay has undoubtedly gone on by now that I anticipate that the tooth is unsavable.

It could be saved with root canal, post and core, and crown; but from the look of it, it will not last you long. I would just pull it, and replace it with implant and future crown.

I would agree with your dentist.  the caries looks deep and if you are already having soreness it may be the beginning of an infection.  Go see your dentist to see if it is till salvageable.  AT least get some medication for the infection/pain.