How can I get my moms trust back?

A while ago, my mom caught me kissing my boyfriend in public and she is one of those people that think PDA is horrible. Then i kept getting detention for being late to my cles. And blamed them on my boyfriend. (it wasn't his fault) Then my mom caught me with smoking. Then caught me with marijuana(i was just holding it for someone. HONESTLY). How can i get her trust back. I tried to talk to her about it, but nothing seems to work. She is always saying she has given me chances but she hasn't. And how am i supposed to get her trust back, if she doesn't let me do anything to prove to her that she can trust me.