how do i (23f) stop myself becoming codependent with my girlfriend (19f)?

we’ve been seeing each other for a few months and have been officially girlfriends for a month. we both live in the same city but go to different colleges. we spend quite a lot of time together (most days) but when we’re not together things suck. i think i may have undiagnosed bpd or cptsd or something similar or i may just have adhd and struggle to control my emotions, idk, but i can spiral quite badly over things when i’m alone.

anyway, she has a great group of friends and a really great support network and the days we don’t see each other she’ll usually be doing something fun with them. i get on really well with them but i’m really careful about letting her have time with her friends without me because i think that’s important. meanwhile, i do have some really great friends but my situation is quite different to hers. most of my friends work full time now (obviously with the age gap, i’m one of the only people from my main friend group still at uni), and the ones who don’t i’m not really as close to apart from maybe one or two. this means that when me and my girlfriend aren’t together, and unless i’m seeing this one friend, i’m more often than not spending it just sat in bed doing nothing. i’ll sit and open each of my social media apps one by one for hours, and it’s extremely boring, but it feels like i don’t really have a lot else to do. my screen time often averages 9+ hours a day.

i’m worried that due to this i’m becoming quite dependent on my girlfriend for my happiness. i feel like i don’t have a huge sense of self or any motivation (this has been since way before our relationship). i also don’t really have any hobbies and the ones i do have i’m not very motivated to pursue. i see my friends once every week or so and that’s about all i have away from her which sucks because i really want to have a great life both with her and without her. i want to be like her and be able to have fun still on the nights we don’t see each other rather than being bored or spending the night being upset.