Crush is taken but flirting with me...

If I knew who his girlfriend was I’d tell her, and I didn’t know he had one until a month after continuous flirting. I called him out on it and he went quiet. After two days of silence from him he started flirting again.

As some of you probably know, crushes can be difficult. Sometimes people can’t speak correctly or be around them without giggling. I’m the latter. It’s bad how obvious it is, but at least the girls know that I was unaware of his fboy reputation.

I promise I am doing my best to stop his advances (especially the touching. lots of tickling doing on.) but this is getting difficult. I care for him as a person despite being furious at him, and I don’t want to straight up cut him out of my life. I just need to know how to stop his advances...

(Edit: we’re lab partners so I can’t avoid him if I try)