coolant reservoir boiling out but temp gauge normal.

What is your question?

so I thought maybe the temp sensor was bad because the res was boiling. when I was under the hood I noticed the top radiator hose felt like there was no water going through it so I replaced the thermostat. same problem. I can still squeeze the top hose and it doesn't feel full of water. the temp gauge starts way below C when its cold then moves up to normal, a little bit lower than halfway between C and H. if im not overheating then why is it boiling?