Leaving someone you deeply love

Me and my boyfriend are doing long distance we are both in college in different parts of the country therefore we go on separate nights out. We started going out September 2018. in June 2019 then a friend told me he was doing drugs he denied it and kept lying until I found proof and then we broke up had a row but we ended up getting back together he kept saying he just did not want to hurt me so that was fine he wasn’t doing any hardcore drugs and just for the record I have never even gone near drugs I just don’t agree with them. all was going well until now January 2020 I have been told he’s doing coke every time he goes out and does a lot of it obviously all the lies, hiding and the extreme abuse of drugs is a deal breaker but I absolutely adore him and I am really struggling with leaving him he’s my best friend and I’m finding it so tough