How to tell if a Sagittarius man is really into me?

He's my co-worker, he's a bit younger than me, but he's always roaming especially around the girls in the company. He's so charming and funny and he has that free spirit in him, he's not tied by any restrictions which I admire, and he's the life of the office. Everyday he comes to my desk, sometimes he teases me by typing randomly on the keyboard or turning off my monitor or startling me by clapping or whispering, sometime he asks about work, sometimes he uses my computer -without permission- to do something related to his work, sometimes he shows me memes on his phone or talk about non-work related stuff, he even showed me pics of his setup -he's a nerd-. I knew he's a Sagittarius cuz he asked about my birthday and my sign and he told me his, he also asked if I was in a relationship at one point. One day, me and my female co-workers ordered sweets and he joined us which wasn’t surprising cuz he always around the girls but he sat beside me, and I sensed he was uncharacteristically nervous. One day, he offered me a muffin. One day he offered to buy me tea -cuz i was coughing- and when I left the money on his desk he gave them back to me with a little tap on my wrist and a low voice saying "I get to buy you tea, not you." My desk is kinda facing the door to the office, so everytime someone comes in or goes out I get to see them. He glaces at me most of the time whenever he enters or leaves. Last time he entered, I glanced up to see him looking at me, holding my gaze all the way until he disappeared from view. These signs might screem "hell yeah he's into you!" But the thing is he jokes around other girls too to the point I feel jealous sometimes. Most of the girls treat him like the younger brother. Personally I treat him like a friend cuz we have a lot in common-gaming, drawing, anime, high tech, cats, etc-. I'm a virgo so i'm always quiet and very introverted, and he’s extremely active and social and very extroverted. What do you guys think?
How to tell if a Sagittarius man is really into me?
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