Shower Pressure Problem
your trouble seems to be right there! Dont forget to remove the water saver filter which is a tiny annoying water restricter saver. it is made of plastic and is usually white, and can be found when you unscrew any typical shower head assembly. it gets even worse when the water saver plastic peice of bunny dew gets gummed up with anything.
The average city in the us wants to make their job easier by saving on the amount of water you use by making it manditory to cut your water usage with a cheap .02 cent filter. Im sure their argument is a good one and they would school you on the savings on your water bill. I for one want that blasting hot shower in the morning to wake up.