I'm not a dentist or doc but were you given any antibiotics by the dentist? Because a person who had bad breath who tried everything did end up using probotics and other things to help her situation and it worked! I'm thinking too if you may need to gargle with perioxide and water, since the hole has not closed take a cotton ball dipped in perioxide and place it on the area and then rinsing with the perioxide and water.

It's possible because if this filling was mercury it may have poisoned your system ( because if you look up mercury fillings they have been known to do that) and caused other toxins to get into your body because of it, you may need some cleansing from heavy metals and toxins in your mouth and body. I know that chlorella does help cleanse the body of heavy metal and toxins and it's possible it may have spread to your digestive site even though you only seem to smell it in your mouth.
What that person did was to take probotics(they have them at GNC) Get the probotic compex with other cultures they have 1-5 billion cells the higher you choose the better. Take 6-7 with meals and also get some digestive enzymes,(To help with food digestion) and an antifungal maybe grapeseed extract(which will help too)take vitamin C (a double dose)which is good against infections. I would either look online for a heavy metal cleanser to detox the body, or start taking Chlorella (they also have it in powder form) and you can mix it in drinks like tea or water but I would stay away from sugar, and red meats until things get better. If you can find a heavy metal cleanser that would be great, also taking zinc (is suppose to be good for odors) and magnesium oxide (works better than magnesium sterate)along with copper,and B 12 or B-Complex, and get a colon cleanser with psysilum (they have the original colon cleanser at most stores) use it once a week to cleanse your colon. Our mouths have a lot to do with our digestive system, our mouths affect the rest of our bodies, because of what we put into it.

I know you may be saying what does my digestive system have to do with my tooth? Well our mouths and our digestive tracts all work together, but I would try this and still do the perioxide rinses and stop chewing gum. And stay away from soft drinks like soda and koolaid they are bad for our teeth. But taking probotics will help your breath tremendously, You mentioned you have taken penicllin which is an antibiotic, when we  take antibiotics they can ruin the good bacteria in our bodies, so taking the probotics like acidophillis will put the good bacteria back into the body. and keep your probotics in the fridge to keep them fresh, I hope this helps. www.watershed.net/spirulina_chlorella_article.aspxThsi site will give good info about the benefits of chlorella and it has info on Probotics too. But you can get those from GNC or any health store online. this may help too. http://bodyodor777.com/myths.html Go to internal causes they have info about BO and the mouth.