want to break up with my gf

context: i'm a y13 girl, applied to oxford, a levels this year.
i'm in y13 and want to break up with my gf, we're medium distance and don't see each other that much. if i'm being honest, i've lost feelings. we only started dating in september, which i think is honestly a really bad time for me to start a relationship. i cant put nearly enough time into the relationship, which isnt fair on my gf. i don't think i can break up face to face any time soon bc it's a lot of effort to organise seeing each other and we won't for a while, but i don't want to continue this relationship. i know my gf won't be expecting it at all though and i feel really guilty, but i can't see the relationship going anywhere and if i cant do this distance i definitely can't do any further distance. i guess what i need is motivation to actually just rip the plaster off, i'll probably have to do it by call. i feel guilty but i also feel guilty leading her on. how do i DO this!! i've never been in a relationship before and i don't want to be the evil ex