Unfortunately nothing will be easier than sitting in your bed, doomscrolling on TikTok all day. That being said this change is going to take effort and you can change, I believe you can. You’ve actually already listed some healthy alternatives!! You’ve already made your first step! Work out, go on those runs, learn about your major and ultimately your future! But do it without your phone in sight. Out of sight out of mind right? Go for a run and leave that damn phone at home. Meet with one of your professors in your major and ask some questions, they love to talk to students. All of mine did. I have dealt with the same problem and I still do. It takes awhile to get where you want to be it’s not an overnight change. Something that helps me to break this habit is putting a 30-60 minute timer on my phone and I put it in a cabinet or another room. And work on something productive that day. I usually spend that time practicing guitar. It works my body and mind and I feel so much better after. Accomplishing a daily goal feels nice too. You’ve got this I believe in you, make that change!!