Feelings for boyfriend Unstable?

I dont know..its like one minute i like him..then the next i think hes ugly and i literally hate his guts..i sometimes find myself looking at other guys and thinking they are hot..i mean we've been going out for about 2 years ON AND OFF. He treats me nice but he's not vey funny..and hes not vey attractive. sometimes on the phone, we'll just sit there and he dosent say anything..Why am i feeling like this?? No silly comments please Thanks