Please Help Me - Bad Breath and other problems.

Hello everyone my name is Tyler. I am 21 years old, and started having this problem in my mid teens (around 15-16). It started around this time with me noticing an bad taste in my mouth. It wasn't that bad at that time however, chewing gum helped it go away. With time it got worse. Fast forward to now years later, I have a bitter metallic taste in my mouth 24/7. Although most often cannot smell it myself, I am positive I have a foul odor coming not only from my mouth but even from my nose when my mouth is closed. The coating on my tongue is a pale white pretty evenly distributed except near the back of my tongue where it is actually a thick white coating that can be scraped off. My other symptoms include extreme social anxiety, which I believe I always had to a lesser extent, with constant fears of my odors making it worse. My mouth is always dry, with bubbly/foamy saliva that seems acidic and I often have to spit out.My other symptoms include constant fatigue, always feeling tired and weak, brain fog with choppy thoughts, depression (though mostly from bad taste/odor problem) and I seem to not be able to gain any weight no matter how much I eat. I don't believe I'm absorbing nutrients . Another new symtpom is a severe susceptibility to cold. Does this sound familiar to anyone ? I'd be glad to provide any additional necessary info and thank you in advance for your time and help. This problem has ruined my life by taking one of its fundamentals from me which is being able to communicate with others. I thank you again for your time.