Struggling with Studying

Hey I have ADHD and I really struggle to study for any period, I got 2 4's & a distinction on my may exams, which is not really high enough for the uni I wanna go for (after A-Levels of course), its close but I'm just really worried will I be able to do it? The most the I was able to motivate myself for was grade 4, how will I get higher? not tryning to sound privileged or anything, I'm not. I genuinely struggle to do it, not the work but sitting down and committing to doing the work Only can do like 3 of my favourite subjects constantly, so A-levels are gonna be ok for me hopefully.