How can I be more positive? (19M)

This might be long but here’s some context, I’m a 19 year old guy, I’m currently finishing up my college semester with a horrible GPA and I’m hopefully starting a new job soon in corrections. I’ve noticed over the past few years that I’m pretty much a buzz kill. I have very bad anxiety and depression that hits at random times and a lot of the time it’s very obvious to others and it affects everyone around me. Whether it’s something small like my mood, or when I’m at a point to where I’m genuinely furious, It’s always noticed and people don’t like it. I hate being seen as such a negative person and I hate seeing it drive away people I could become great friends with. I don’t wanna always be the guy who’s angry with an excuse as to why people don’t wanna be around him. If anyone has ever been in the same boat I’d really like some help. I feel lonely and I want things to change.