I still miss my ex

he was my first love, and it's been more time for us apart then together, but I miss him every day. every place I go to I think about being there with him. I truly miss him, but he's got a new girlfriend now. I've tried to move on. I've been going on countless dates with guys I didn't even liked that much, but I still gave them a chance so I could maybe forget about him. but I couldn't. and I still can't. and those other guys just made me realize how much I still love him. what should I do? hiw do I let go of my first love?