Asking for Help to Be a Better Muslim - Feeling Lost, Salam

Salamualaikum. I've wanted to improve for as long as I can remember. As a child I was scared of doing wrong, but growing up and seeing the world around me made me doubt my faith. Sometimes I worry: what if Jannah isn't real? What if I'm wasting my one life on something that's not true? I desperately want to believe in Islam and quiet these thoughts, but I don't feel worthy. I feel like a terrible Muslim - maybe I shouldn't even call myself one. I don't pray regularly. I struggle with chronic masturbation and a lot of impure thoughts. I swear a lot and keep doing things that go against what I know is right. I feel ashamed to pray; I don't know why. I'm afraid my parents or friends will judge me, so I don't want anyone to see me praying or know that I'm trying. My mental health is a big issue too, and I haven't really turned to Allah except in emergencies. I only make dua when I'm sick or in pain. Other times I'm selfish and don't give Him time. I don't know where to begin. I don't even have a proper prayer routine yet, and when I try I worry I'm doing it wrong or that I'm unworthy and being judged. Please, can anyone give simple, practical steps or duas to start? How do I stop feeling ashamed of returning to Allah? How can I build consistency in prayer and reduce these habits and thoughts? JazakAllahu khairan for any advice.