How can I start to trust him?

I need help! Here's the deal :
My boyfriend and I have been going out for a year. I love him and he says he loves me but, he's always making me jealous and when we go out. He spends the night off with other girls. I don't trust him very much and he has changed a lot. he says that 'we don't need to spend every minute together' and don't get me wrong I'm not a stalker or someone that always wants to see him but more than once a week would b nice. We used to spend every day together and now we don't, I don't understand because he says he still loves me

dump him
he is scum if he is stayin at other girls houses
thats just not right and no girl
deserves that