My dad is an addict & my mom’s staying with him. I don’t know what to do

My parents divorced 10 years ago. My mom (39 y/o) was granted custody of me, (18) because my dad (45 y/o) had a history of substance abuse. Back then it was pot, alcohol, and cocaine, but he kept it under control. At the time, my mom said that he told her about all of his substances & that he was in control. She’d borrow some of his pot every so often, and so did I throughout my adolescence. After they divorced, he started using more and worse substances. Probably about 4 years ago, my dad was going through a really rough period. He had a drug-induced mental breakdown, got diagnosed with OCD and GAD, and he tried killing himself a bunch of times. He was kicked out of the house, evicted from his apartment, and lived in his car for a while. All of this was during high school, but it got significantly worse once covid hit. The drugs and mental health just got worse and worse. Evidently he met a dealer and started buying oxys. When my mom found out about it, six months ago, she kicked herself for not being there for him and took me out of the picture so I wouldn’t blame my dad. She wasn’t worried about me because I’d only smoke pot, but just in case, she didn’t want me around him. So she helped him plan a trip to rehab and stayed with him until he left. When I got home from an acting camp, she told me the whole story. <br><br>I wasn’t expecting her to leave me out of the picture, and it hurt. She didn’t even tell me about the breakdown or getting kicked out of his apartment. I didn’t know my grandpa died a year ago until I talked to my dad last week. It felt like she found out everything about him while I was separated from him. She didn’t even tell me how bad the situation was. Now my mom’s staying with my dad again and she’s still hiding me from her son. I didn’t think he was at fault for his drug use, but she still won’t let me see him. I don’t know what’s going on or if she even cares about me anymore. I don’t know if I’m allowed to talk to my dad, and I don’t know how to help him. I just want to see my dad.<br><br>Edit: I know some of the comments are rude. I don’t condone abuse of prescription drugs at all, but I think they’re the best way to deal with my dad’s situation. I’ve heard him talk about going cold turkey once, and I don’t want to hear that again. I know that he isn’t responsible for the addiction. <br><br>Edit2: Thank you so much for the advice and kind words. I’m going to talk to my mom about it. Whether or not my dad would want me to know, I just want to be there for him. Thank you again.