Seeking Allah's Help to Break Free

As-salamu alaykum, brothers and sisters. I've been struggling with cannabis since I was young, and for a long time, I smoked heavily every day. Alhamdulillah, I'm now trying to return to my studies and strengthen my deen. Since Ramadan, I've been making a consistent effort to pray, often managing three or four times a day-a big step, as I used to not even fast. But the struggle is real. I still find myself smoking many nights. I managed three months clean, then fell back into it. I've thrown my supply away so many times, only to go out and buy more. I recently had another two weeks of sobriety, but I relapsed today. Even during this blessed month, I've been feeling very emotional and anxious daily, and I went back to smoking right after Maghrib. How do I stop this for good? When I'm sober, I feel like a terrible person. I've, by Allah's mercy, stopped using harder substances, but weed feels impossible to quit because it's so easy to find. Adding to this, I have my final university entrance exams in three months, so starting to smoke again now is a really terrible idea. I'm asking for your sincere advice and du'as.