Nah mate your not depressed!!!
I guess you could say the honey moon faze is over in your case again!! Its quite natural to have the feelings your having. You feel that he is the one that you want to spend the rest of your life with but what if your wrong? I have these feelings almost everyday and i'm still not quite sure.
You say that you wouldn't be bothered if you and him broke up but I bet the thought of being on your own absolutely scares the crap out of you.
Its just a faze babe, it will come and go trust me!! Its went you cant stand him touching you, the sight of him or my bad habit when i'm not happy in a relationship I cheat on him!! Haven't done that in the 4 yrs my partner and I have been together so i'm going good so far.
Cheer up!! :-)