well our galaxy isnt so big that the light of its stars hasnt reached us. but yes it is possible that the light from some star that are over a trillion light years away has not reached us. but if the theory of the big bang is true then at some timethey would have been very close to us and so there light woulda reached us then and since they are nto moving away from us at a speed greater then c there light should always be able to reach us.

the human eye is extremely sensitive but your right we may not be able to see a single photon in a sea of black. however if even if 1 photon from each star reached us then the combination of all those photons would result in something we could see. the difference here is we probably wouldnt be able to tell that the light was coming from more then one object.

and I thought space was empty what could be blocking so much of that light.

those were 3 pretty good answers and your on the right track. but not quite there.