Phobia's are really hard things to live with. Especially ones related to our bodies and germs. I used to have a phobia that people were trying to poison me and refused to eat or drink out of anything I hadn't washed and prepared. talk about embarrasing!!! I got over that through CBT and hypnosis. Now I try to never do dishes!!!
I'm really sorry to hear how fearful you are about this. By all means wear the mask and let your doctor/nurses know your concerns. Are you able to take herbal anti-nauseants that will lower your risk of vomiting? Once that won't affect the SSRI's? I have IBS and find them really useful when my stomach is a mess.
Again, I remember how difficult this is. Please be kind to yourself and let us know how it all goes ((((hugs)))))