Separation Anxiety with my Partner

hey, since i (18F) graduated highschool a few months ago i've been noticing my separation anxiety around my girlfriend getting much worse. i struggle with those annoying feelings of dread and uneasiness when i know i'm going to have to spend even just the majority of a day away from her. The longest i can go without feeling shitty from a lack of her presence is honestly only a few hours, it's gotten pretty bad since we started living together at the start of this summer.

a couple months ago she took a trip that lasted a week and i was an absolute wreck, like a shell of myself, and i don't know how to just be normal without her.

i feel so guilty for being this overdependent on her - i know it's just my routine adherence, but i just want to be able to give her space without reverting back to clinginess the second i start missing her.

probably worth mentioning that i don't force her to stay with me 24/7 or anything of course, it's just that i can't not feel shitty when she does leave, no matter the reason. The problem is really just the lack of her physical presence, as she's become deeply ingrained in my routine.

how do you guys deal with this stuff, or with similar issues?