Why won't my boyfriend accept me as a friend on facebook?

I’ve been with my boyfriend for a year and he has had a facebook account he never used. Recently I requested to be his friend on it but haven’t been accepted. I thought it was because he’s never on it and hasn’t seen my pending request but I’ve just found out he added his ex after I requested him, meaning he’s seen my request but is ignoring it. What should I do? He also spends a lot of time on his mobile, never leaves the room without taking it with him and becomes very jumpy if I sit down next to him while he’s on it. His behaviour is very suspicious and although I know I need to confront him, I’m araid of opening a can of worms that can never be closed.