Yes, that is all very weird. And–more importantly– hurtful to you. In fact, I would say what you have is not a real relationship. At least in his eyes anyway. He is casually dating you while still keeping his ex in the picture.
In fact, he might still be sleeping with her. The fact that he refuses to let you go on his Facebook is a bad sign. You shouldn’t have to go through his phone if you trust him, but he’s not exhibiting particularly trustworthy behavior. There’s definitely still something going on here with the ex. At the very least, he has feelings for her which he’s deemed more important than what he has with you. The fact that he won’t tell her that he’s seeing someone is a bad sign.
After five months, the relationship has moved past the casual stage. You should have a sense of whether or not this guy is right for you. Someone who is still tangled up with their ex to the point of banning you from Facebook and hiding your relationship is not right for you. Period. This guy is exhibiting all the signs of someone who still has unresolved feelings for his ex, could possibly be cheating, or at least has some leftover relationship baggage. It’s time to confront him on this, and consider whether or not the relationship is worth salvaging. If so, he’s going to need to make some big changes. Like, for instance, officially breaking up with his ex. Cause right now, he’s technically involved with two women at once