What shall I do about the relationship?

What shall I do about the relationship? Do you think I'm better off as just friends with him? I'm 26 dating a 37 year old man. We agreed to try an open relationship. He has done a lot for me. Lately he has been concentrating on flirting more than us. We have been dating for 6 months. I am needing more time to think about the relationship. At this point I don't know what I want to do about it. We both don't want it to end but his flirting is getting a little too much. We both met at work fell in love now he has a major crush on this girl Stephanie who helps out at work. He's always talking about her. I think there are signs that he might be loosing interest in me already. There is a reason why he's 37 not married since he's a big flirt. Marriage isn't for everyone. We agreed to slow things down. Maybe we should take a long break from each other see what happens? I want to save the relationship. He is always saying he loves me I know guys are guys they're always going to flirt at times.