I'm sorry to hear that you're feeling this way about yourself and your insecurities. Do you feel yourself falling into a depressive weight because of your body image, or something else?
It's great to hear that you're a sporty person, and that you're playing basketball and considering boxing, those are some really good and healthy sports to be picking up (especially boxing as that helps releases stress, and if doing it with a trainer, it can help motivate you).
I found setting myself some realistic and creative goals to be really helpful with keeping me motivated. I'm also overweight and would love to shred some fat as well. Every year I set myself an incredibly impossible resolution to lose weight, and never able to achieve it. When that happens, I feel disappointed about myself, and it brought my self-esteem down a lot.
But this year, I thought I'd do something different. Instead of wanting to lose weight, I set myself a goal to run a 5km marathon, and follow an 8 week training schedule for it. The training schedule teaches about simple healthy eating, making sure to have resting days, and a weekly target in terms of distance to run that week. I definitely struggled the first week, and even a short 1.2 km was a struggle for me. But each time I reach my target, I gave myself a pat on the back and told myself that I've done well. I'm currently in my 4th week of training, and I'm way ahead of the weekly distance target. (This week was meant to be just 3.8km, but I managed to run 4.8km). It help built my confidence a lot, knowing even though I'm overweight, I can still exceed the training schedule.
You must be wondering "where's the weight loss in this?". To be honest, it became more of a secondary thing. Because I know by running and eating healthy, I'm keeping my body fit and healthy, which is all that matters to me. There's certainly 1 or 2 cheat days where I eat things I like such as burgers and chips, just to keep myself happy (yes I love food). I also weigh myself at the end of each week, and if I do find myself losing weight from my running, then that's a bonus, and not a goal. The important thing is I hit my running target each week, which is going really well at this current rate, and aiming to do a 10km marathon after this 5km marathon.
I hope that gives you some ideas on how to stay motivated and make progress. Happy to chat with you more :)