First of all, welcome!
I'm pretty new myself but have found this to be a great site for motivation and support.
Kickboxing is a great workout! And congrats on your clothes already being looser
As far as diet, I've said this before here, but my fav diet I've ever tried (and I've tried almost all of them from WW to Atkins to South Beach to Slim Fast, etc..) is the Richard Simmons diet. It's on his site and a cheap kit. I've only been successful with his because it teaches, and forces you, how to eat correct portion sizes as well as a balanced diet. If you've eaten all your protein and carbs for the day you may look at your "food mover" and see 2-3 open fruit windows. It's a good reminder of what you're lacking. I needed this because when I just calorie count I don't include enough healthy stuff. I wind up only eating carbs
Definitely recommend that, but no matter what, be proud you're here and on the right track! I am!