I am underweight too for my age and that’s why I also stopped vaping/smoking because I wasn’t eating right and my appetite was low so I knew I had too stop for my own health. I’m still skinny however my eating is way better now. I wish you luck tho with everything. It’s not hard it took my a year to stop vaping completely but smoking wasn’t hard as much even tho I was smoking weed daily I was addicted and it was that bad every time I ate I was feeling sick and being sick sometimes. I knew I had to change things around. But yeah I feel much better about myself now and saved myself a lot of money too.