Actually, I'd say it depends. Giving another man a hand job, most would agree makes you gay, no? But giving yourself a hand job doesn't make you gay, it just means you're masterbating. So the act of touching a cock doesn't make you gay. So you can't simply say touching your cock with your mouth makes you gay, that would be somewhat hypocritical.
What is it that makes someone gay? I wouldn't say simply touching a cock makes you gay. It would either have to be physical attraction to
another male (because finding yourself hot wouldn't be very gay, now would it?), but would touching
another male's cock with or without physical attraction be gay? Most would say both with and without physical attraction would be gay. But that can't be brought over to your own cock, as well, since that would make the entire male population homosexual.
So, really, what is the definition of gay? It seems you're making the spectrum a bit too wide