I want to fuck my best friend.

I met him when I worked at a retail store. He immediately started to follow me around the store and talk about himself and ask questions about me. He moved for school and then I started working at another corporate company. Out of the blue he starts texting me and asking to “chill” which I didn’t think anything negative could happen with just chilling with him. One day turned to two and then three. Fast forward 2 years and I break and tell him that I like him more than a friend. He tells me that he’s flattered but he’s straight. We continue hanging out and talking on the phone like nothing happened. More time lapses and again I tell him what’s happening with me towards him. He again states that he’s straight. At this point I stop holding back and literally treat him like my life partner and he does the same to me. He’s straight then why does it feel like we’re in a relationship and we argue just like a regular couple. Is he gay and interested or am I delusional?