Fickle 1994 Camry not starting

I have a 1994 toyota camry. some days it  starts some days it doesn't. when
it does start, it runs great for a while. I can always tell when it is about start
the no starting thing again, because the check engine light comes on dim
when i press on the gas, and gets brighter the harder i press.  when it
doesn't start, it always will after it has sat for a few days. the longer it sits, the
longer it ends up running for before it doesn't start again. also, when i press
on the gas, the speedometer doesn't go up very fast or far, like i could be
flying and the highest that it will register is 40. and the rpm does the same.
yet it is still counting mileage. HELP!!!!