weird guy idk what to do

Theres this creepy guy in my college lab class. Im a nice person and never intended to lead him on. Well he obviously likes me and is very strange and keeps hinting how i should date him. What he doesnt know is i have a bf of 2 years. I never flat out said this because i never thought it was important. Honestly im scared of how he will react when he finds out. If he was my friend on fb or anything he would see my profile pic is my bf and i kissing. I dont know this guy well. Im in a study group with people and he always invited me which i took as friends. I just am nervouse because hes a lot older than me and  he just has a bad vibe. Im going to always call my bf when i go to my car now and all but any other advice?