Sometimes my truck won't start

Sometimes my truck won't start and now
it's happening every day.  I don't think it's
the temperature because it happens when I
haven't driven it but I could have just turned
it off a minute before. It turns over and only
starts if I press the gas but won't stay
started if I don't hold the gas steady for a
minute or two or Rev it a few times. It
makes a screeching sound every other time
I try to start it. I have a leak in my power
steering.  Don't know if that's relevant but
thought I would throw it in there.