not printing whats on the screen

Hi have a new envy4502 printer but it only prints part of what is on the screen - sometimes leaving large gaps in between print, sometimes printing pages 1 and 3 of 3 then the next time 2 and 3.....  I need to get homework printed tonight but all it gives me are is the first part of printing, a large white gap then a couple more lines then says its done.  Thats not whats on the sceen.  help pleas