I think we might have skipped a step¿

Okay so I started my new job in November and my 2nd day there this guy swept me off my feet. at first I was a little taken back by how fast he approached me and how sweet he was being to me the first day he met me. He had asked for my number and everything. I don't know exactly what I was thinking, but I gave it to him and ever since then him and I have been a team. He is the funniest, nicest, smartest, most genuinely kind hearted man I've ever met and I'm so glad he swooped me up as quick as he did. We've only hung out outside of work twice but it's only because we both are ALWAYS working. We both are on a mutual agreement that it's just us two and no one else but we've established that in weird ways. For example, he'll cop a feel when no one is around and say "that ass is mine" and I'll just laugh and then he'll proceed to walk away and turn around and be like "it's all mine right?" And I always give him a reassurance that yes my ass is all his, and vice versa. So he hasn't asked me to be his woman yet directly but I don't know if I'm just suppose to assume that because he and I normally already know what each other are thinking. But I don't think I should assume on this. And on top of all this on my mind, yesterday we were laughing and making fun of people and out of no where he said I love you (but keep in mind he and I are always playful and almost never have serious moments unless, we're being intimate of course) and I said it back. But I didn't think anything of it until later that day I was being sassy with him and he replied back "I declared my love for you today and all you throw back at me is sass?" Of course he doesn't talk like Shakespeare or anything that's just how we speak with eachother, like a playful disbelief "how dare you" type of thing. We tend to slip into theatrical mode sometimes which I find hilarious. Anyway I feel really stupid for asking but what do I do? I've been hesitating to say anything just because things are going so well. It's not that I'm scared to talk to him, he's my best friend I tell him everything and there isn't anything I can't talk to him about, it's just I literally can't put into words what exactly my question is. Please help!