IF there were no evidence of God, then faith would certainly be a delusion. Delusion is simply someone believing in something that is not true.
IF you truly believed that all miracles can be explained away by science, that all folks who performed miracles were charlatans, and Jesus was just a crazy person who let himself be assassinated or totally made up, then faith may be simply be mass hysteria.
Freud call us religious folks obsessive compulsive deurotics. That would be a valid diagnosis IF everything we believed in were not true. BUT the fact that many or even all of the things that we believe in are true, makes us nothing like that.
THroughout Jewish and CHurch history there have been many prolific miracle workers, St Padre Pio being one of the latest in the 20th century. IF indeed all of these wonder workers were frauds (including Jesus) or delusional, then yes, one could conclude that faith, Our faith in particular is delusional. I happen to believe that many of these saints, especially Jesus and the Apostles were the real deal. Some of the things that the more famous miracle workers did is really amazing. Read up on a few, I think it will help you regain some of the faith you once had.