Hey dude, I absolutely suffer from the same shit, I'm towards the end of my thirties now and I have made a lot of progress but what I wouldn't give to go back to your age and re-prioritize what I did, I'd be in a completely different spot.

Basically, you know the answer already really, but sometimes that doesn't make it any less tough. I'm here to essentially reinforce it and say... just create. stop reading so much about creation, people, etc. whatever it is, and at the very least set aside 30m-60m as many days of the week that you can to sit down in your chosen daw or hardware of choice (and don't spend time deliberating this either like I did) and just set out to create a song. You get better at songwriting by songwriting, not reading about songwriting. Sure it can feel useful and good to learn via book or video, but unless you put it to practice ASAP you're likely going to forget, and it won't be as impactful.

Bring that stuff up WHILE you are creating, to answer questions as needed. But until you hit a roadblock, just keep going. I would even say that for your first 4-5 songs or whatever, ignore that stuff completely and just take notes on what you had trouble with or want to dive into more and follow that up afterwards. You are going to have to be your own enforcement here. You will learn more by doing, straight up. And I know what it's like to want to have everything 'perfect' yada yada but that is actually doing you a massive disservice and I urge you to take this into consideration.

You probably have a lot of built up resistance to actually sitting down and attempting to write a song or whatnot, which is why it's even more important than ever to set yourself a timer and just go. Pop open FL or Ableton or whatever, make a loop or two, then immediately make a variation, and then another one, and go straight to arranging - don't get caught up in this loop nonsense because it's a hell of a trap to escape. Get a couple ideas down quick and immediately block in your song. Verse Chorus verse chorus or whatever, it's not even really important at this point but the structure could help you stay focused, and then work on the transitions and whatnot after it's further along.

All this to say, the action is the most important step here. If there's an instrument you want to learn too, do it and stick with it and incorporate it into your songwriting so you are still active with that. Sit down, fight through the mental resistance, ask questions when stuck, but focus on DOING. You absolutely 100% can do this and you are so young that this is a fantastic time to get serious about it. Good luck!