Journey Guitarist's Wife ... PISSED!

Journey guitarist Neal Schon married 1986 Playboy Playmate Ava Fabian just TWO MONTHS AGO -- and she tells TMZ, she's absolutely devastated by her husband's affair with Michaele Salahi.

Ava -- who claims she was with Neal right before he went on tour, tells us, "This is very painful for me. I'm very hurt." It's pretty clear from the video ... she never suspected a thing.

Ava and Neal got married in Paris in July -- and as you can see in the pics, the entire band was there.