Is there a limit to how many feeds can come out of a junction box. I have a 4" metal box in my attact for my bathroom, Id like to run one feed for the receptical, one for the vanity light and one for recesed lights / fan. I s this OK?

Everything about the electrical trade has maximums and minimums.

Here is an explanation on outlet box wire fill:

Box Fill Calculations (http://ecmweb.com/nec/code-basics/electric_box_fill_calculations/)