Should i try or just forget it?

There is this boy in my gym cl and we have been talking for a few weeks.Problem is he has a girlfriend. Whenever i like a guy who has a girlfriend i forget and move on. I really like this boy and i don't want to try and get over him. Whenever we have conversations he makes me think about something a different way. Hes so open-minded and understanding. In cl i hang out with him and his other two guy friends. In cl he will flirt with me and i try to show i'm not interested but he sees through it. One time he even laced his fingers through mine so we were holding hands. I pulled my hand out and gave him a look. He just smiled and apologized. Other times he will make really suggestive things but hes just joking around. But when we were texting today he said if he didn't have a girlfriend he could imagine me his girlfriend. I asked his one of his friends in cl and asked what was up. His friend said he was confused and in cl forgets he has a girlfriend. If he broke up with his girlfriend and we eventually were a couple i don't know if i could trust him. If this could happen to his girlfriend when they went out it could happen to me too right?