Anyone have success turning their bad health around? 😅

Hello! Little background. So I'm 23 years old and I've hated water all my life. I hardly drink it ever. I have a lot of caffiene (dr pepper, monsters, coffee, etc). My diet sucks too and I'm not active. I gained like 50 lbs in a little over a year and I'm feeling super shitty about it. I also smoke quite a bit of marijuana. I dont have any major health problems (knock on wood) and I'm hoping its not too late to turn my health around. I'm almost even scared to exercise fearing my body won't be able to take it. 😅 That sounds irrational but thats how I think. Anyone have any health tips or ways I can transition into a healthier lifestyle? I appreciate it. 😁