How Should I Break Up With My S.O?

Hey all. Fair warning this might be kinda long but I wanna fill in some of the background details.

So I’ve been in a relationship with my girlfriend for just over a year now. We’re both 17 in grade 12 and about to graduate high school. Ever since I was probably around 13 i’ve struggled with my mental health in terms of some pretty mild depression and anxiety, nothing too serious. Covid started half way through grade 10 for me, and it was around that point that I started to smoke weed. I developed i really strong dependency on it where I couldn’t eat or sleep without being high, and this has went on until recently. I’ve tried to quit a couple times but each time i’ve relapsed within days, these attempts were usually because I wanted to be better for her; and I would keep her in the loop about how it was all going on these attempts. Throughout our relationship she has often told me the whole, “I wouldn’t know what to do without you” or “if you left I would be a mess”, and that kinda thing. We have completely different goals and aspirations, so I know that unless i’m willing to give up on those for her (which i’m not) i’ll have to leave eventually.

Now that the backstory is set I can move on the the important stuff. So when we started dating in grade 11 I quickly noticed that I wasn’t as depressed or anxious as I used to be. My anxiety hasn’t really made a come back, but at around the 7 month mark in our relationship I noticed that depression was taking a toll on me. I started to become extremely depressed, daily suicidal thoughts, etc. I originally suspected it was something to do with the winter, but over time I realized that i’m being completely drained by this relationship.

Side note. So I have a surgery in a few days, and her family has covid, so I haven’t seen her, or really talked to her too much in the last couple of days. Because if I got covid I wouldn’t be getting this surgery. She says that not seeing me is really taking a toll on her, but even if i hate to say it it’s the opposite for me. Even though it’s only been 5 days, in these 5 days I’ve stopped smoking weed without much difficulty and barely even any common withdrawal symptoms like less appetite or insomnia. I didn’t tell her that i stopped, and it wasn’t really a huge conscious decision it kinda just happened. I don’t plan on telling her. Also, I’ve been able to spend time doing the things I love most like skateboarding and chilling with the homies because all my free time is usually spent with her. I’m noticeably less tired during the day (family/friends mention it), I feel less run down, and i am so so much happier overall where i’m not depressed or having suicidal thoughts.

Even just texting her, or seeing her in class, or having short conversations completely ruins my mood. For example when I was typing this up she facetimed me and asked me what was wrong about 18 times (each followed up with an “are you sure, i care about you/i’m worried about you” after i said yes), and i’m literally the happiest that i’ve been in a year, when i’m not with her that is. I have to break up with her at some point but I don’t want to have to put her through all the works that she always talks about because i do care about her and i still do love her. If anyone has some advice on how to let her down in the easiest way possible i would be very grateful.

Thanks!

TL;DR- girlfriend is hella clingy to me, but the relationship is draining me and I need to find a way to end it with her without destroying her.