Is he interested in me? or am I crazy?

Alright, so lately, I've been very confused with how this guy I work with treats me. I can't tell if he's interested in me, or just wants to be my friend. The biggest aspect of our relationship is the constant teasing. He does it to me so often. Everything from how I do something, to my personality. He always wants to get a reaction out of me. His latest was that he watches a Tv show, and he said a character that's really nerdy and innocent reminds him of me. He thought it was hilarious, and kept bringing it up. And I was acting as if I was mad. Another thing, he always wants my opinion on things. Like if he wants to buy a certain shirt, he asks me if I think it'll make him look good. Also, he asks me a lot of questions about my life, and wants to know about me it seems like. Whenever I get to work, he seems happy that I'm there, and whenever I leave, he always seems sad. Like the other day, I was leaving, and he was like "Please stay longer." and I was like "I can't stay, I have something right after this". and he was like "Okay, I understand...but I can't say I'm not disappointed". So I don't know. I wanna say something, but I don't want our relationship to be weird if I turn out to be wrong. So do you have any input? This is all I have right now, but we've only known each other a few weeks. Thank you so much!