You are having it really really rough. Having to be jovial on the outside, while you are desperate on the inside is torture. Believe me, hundreds of others have been there too. If you were a mild case, i.e. can mange cubicles but not urinals, then it is feasible to start desensing in quiet toilets. If you are moderately to severely affected, i.e struggle to use cubicles, or struggle in other people's houses, it is difficult to get off the ground.
Mark has already made the point about workshops; there we give you a safe environment where you can experiment by controlling precisely the practice situation. There you can cautiously get off the ground, in small steps, with encouragement, and with guidance from someone with experience in doing this.
You are right that in the long term you could suffer mental harm i.e. depression, if you continue as you are. In effect you have nothing to lose and everything to gain by giving it a shot. Get in touch by email (see the contact email address at the top of the page) to explore this further.