What happens when you don't get time for yourself in your relationship?

Me and my girl hang out almost everynight and I just don't have "me time" anymore. I've been feeling a little down and i feel like i've just been detached from my regular life because I've been spending so much time with her. I really like her and I'm falling in love with her but is it normal to want some time to myself sometimes? Tonight is really the first night weve spent apart and it feels great just to chill on my own and have some me time for once. Can you become depressed by spending too much time with your boyfriend/girlfriend?