Foul Breath/coated tongue

I've been plagued by bad breath and a coated tongue for years.  I've spoken to my doctor on several occasions, my dentist and each and every time I've been fobbed off.  No-one seems to take me seriously, but this condition has gone on for so many years without any effective treatment, that I'm becoming quite desperate!  I dread certain types of social occasions, when I know that I've got to sit close to people and I'm absolutely paranoid that everyone can smell it. I'm sick to death with speaking to people who place their finger underneath their nose to block the smell.  I'm sure they think they're being kind, but I'd rather someone said something quietly to me, as unfortunately (or fortunately) I can't smell it myself. I brush 3 times a day, usually floss (though not daily at the moment) and use certain alcohol free mouthwashes. I constantly chew gum or have some strong smelling aniseed cough drops that I use.  I've been to see an ENT specialist to see if it was post nasal drip, he said it wasn't but referred me to another specialist today, who deals with severe mouth/jaw problems.  He gave my mouth a thorough examination and said that he was shocked by how many fillings I had, but I definitely had lots of problems with old fillings that needed replacing and possibly a crown that needed replacing, that could definitely be the cause of all my problems.
I'm so angry that I've wasted so many years asking my dentist for help and they haven't helped me at all. I'm now going to have to find a private dentist (don't trust my current one) and pay to have the vast majority of fillings replaced together with the crowns.
I'm just hoping that after all this work this awful smell will go away - has anyone else had lots of work done only to find the bad breath, metallic taste and coated tongue is still there?
Interesting neither the ENT or other specialist could smell anything when they looked into my mouth - have I just become so paranoid that sometimes I imagine it?
Any help or advice would be really appreciated