I would calmly sit down with him.. express how much you love him. Then follow with how the lying and hiding isn't a healthy relationship, it is causing you to feel uncertain and jealous, which isn't good for the relationship either. Tell him that he needs to decide right now and forever who he is gong to be as no woman would be ok with his current actions. That you love him, but if he is not willing to work on himself and your relationship together, then he needs to move on. To continue this way it is isn't fair to you and you deserve to be treated better. Give him one chance and be very clear. Tell him, you hope he is willing to do what ever it takes. After that, it's all up to him. If he messes up.. move on.

Trust at this point is hard and will take time. Depending on what he says after talking to him... if he is willing to work on it, take a deep breath anytime you feel jealous and instead see if he is trying. He may have to tie up loose ends with other girls... allow him to or they'll be contacting him.

Open and honest relationship ( if he feels the need to hide anything, then he knows it's not right)
communication (he may be feeling insecure about something, what?)
devotion (Only you, what ever it takes)
love (will grow stronger if you can get past this)
effort (You can't control his effort, only your own)
trust (as much as you can, it will rebuild as you see him try)