I have ~/.bash_profile which I would like to be invoked every single time a new GNU screen is created so that all my aliases work in GNU screen as they work in terminal.
At this time this is what my ~/.screenrc looks like.
hardstatus on
hardstatus alwayslastline
hardstatus string "%{.bW}%-w%{.rW}%n %t%{-}%+w %=%{..G} %H %{..Y} %m/%d %C%a "
The problem is a little vague; shell startup files are run by screen upon creation of windows, that yours aren't feels like something is misconfigured in your .bashrc or .bash_profile. I haven't run into this using screen on OS X.
Have you tried iTerm instead of screen? I use it exclusively on my Mac and then use screen on the servers I admin.
shell -$SHELL
Add the above line to your ~/.screenrc, this will make screen start-up using a login shell which will load your ~/.bash_profile.