Why is this happening????

So I never like to ask for advice or talk about these things with people but I’m in desperate need!☹️ So I went to a little get together a couple of weeks ago and sort of started crushing on a guy that was there and hat I also work with. I don’t remember much from that night but I do remember how sweet and caring he was to me. The problem of this whole situation is that I also work with his mother and his sister and me and his sister are really close friends. I don’t wanna hurt her so I refuse to tell her about this. He’s going off to college in 2 weeks and I keep saying just keep swimming.😂 But fr every time I see him it gets harder to work with him. I just don’t know what to do. Should I just keep swimming or tell him how I feel???😓