Hey, don't feel down, I'm about the same age as you so I know what you're going through. Hveragerthi gave some good advice so you can follow those. One thing to note is gerd-- this shows that your digestive system is not in top condition, therefore it would be safe to say your breath is related to it, as you had noted.
In that case, the first thing to target is your diet. Have you tried cutting out dairy and gluten yet? Also eliminate any other foods that you feel more uncomfortable than others after eating, such as meat. Instead, add more raw foods like vegetables and fruits. Avoiding cold foods and liquids will help your digestion as well. If you are taking medications it may affect your digestive ability, I don't know what you're taking but do avoid NSAIDS at all costs.
I found that exercise rid of my bad breath and decreased my odor at the time being. Plus exercise makes one happy (: So increase exercise time and do not! lie down or sleep right after you eat.
If you looked through the forums there are countless amount of supplements that people claimed made them feel better, however since our conditions and its severity are different from one another you will find that what works for others may not work for you. I do recommend glutamine for the gut lining, Zinc as Hveragerthi mentioned, Multivitamins, and probiotics. For the probiotics, I noticed that taking multiple times the recommended amount provIded greater effects. When you continue searching through this forum you will find some others that you may want to try.
Last, if all else fails, you can try a detox/flush. Before you start one please make sure you are not underweight/malnourished, you do not want to hurt yourself further. I don't want to label your symptoms and say "you have Candida/parasites/etc" so I can't recommend what flush you should try.
Anyway, good luck! I hope I helped you to path a way to start finding a cure to your problem.