What did I get myself into??

So I’ll try to keep this to the point. I’m looking for advice from unbiased point of view.

Jan 2017 I started flirting with my now SO. In Feb we started dating. Everything was great! Until about July 2017. He started getting distant... not wanting to hang out or stay over at my house, sometimes wouldn’t even hang out on days we were both off work. For 3ish months we weren’t having sex (which was strange because before then it was almost everyday). We got thru that tho.

Fast forward to Jan 2018. I found out he was smoking marijuana. Which from the very very beginning I have said I am 110% against drug use. Feb I finally confronted him because I had enough evidence that he was an avid smoker. He lied to me for an entire year about his drug use. It was to the point where he spent about 2/3 of his paycheck on pot.

Also in Feb, I found out during the time he was being distant from me, he was texting an old friend. Nothing happened between them physically, but he was having a hard time lying to me about smoking, he didn’t have to lie to her.

Since then I have told him I don’t want to be around (in the same space) any kind of drug, I wasn’t given the choice, this weekend when he smoked in front of me after telling me he wouldn’t smoke again that day... if I knew he smoked when we started talking I wouldn’t have been with him at all. He says he will stop. But he’s said it 3x

The only reason we fight is because of his marijuana use. He never brought it around me, until this weekend. He took my choice away from me. My choice to not be around it...

I try to walk away, but I love him. Everything else is fine except that I feel like he can’t respect my desire to not be around an illegal substance. I’m not sure how to approach this a different way or if it’s even worth it to keep trying anymore.