I'd consider spending more time on the planning and outlining phase. Maybe also start with a short story and go from there. If you know what the beginning, middle, and end of your story will look like then it will just be a matter of writing it when you have the time and motivation.
Starting with short stories that take only a day to a week to write will also allow you to add some finished work to your portfolio while building your confidence and writing stamina. When you get a few dozen short stories done and feel more confident, then try writing a novella of about ~25 chapters from beginning to end. Even if you only write a chapter a day you'll be able to get a book done each month.
It's also worth considering that the style of writing you are using might not be the most appropriate one for you. I started writing stories in highschool and was trying to write novellas in first person present tense and was chasing the trends of what was popular on Wattpad at the time. I'd always feel like it was a chore to write and would struggle to finish what I started.
Nowadays I write third person present tense and only write stories I'm really and truly passionate about. In the past I'd change POV rather often, so writing in third person makes it more natural feeling while I'm still able to monologue a ton. My writing style isn't for everyone and some readers don't like it, but I decided to try it after seeing it in light novels and web novels a ton and it worked!
I also started doing more planning and outlining for my story. I used to just wing it and would constantly feel overwhelmed and unsure of where to start. There was rarely foreshadowing and the writing wasn't the best as a result. Nowadays, though, it feels easy and I never struggle from writer's block. I just sit down once every week or two and write a list of chapter names and a short list of topics to cover in the chapters. Then, when it's time to write, I already know what I'm going to be writing so all I have to worry about is making the time to do so.
I hope this helps!