My hair was about as long as yours two years ago (my profile picture is somewhere in between my long hair and now-hair, it was also not the best hair day xD so not much volume then) and it had the same problem. Then again, back then I didn't know how to take care of my hair xD Anyway, I slowly started cutting it shorter and shorter throughout the years until now it's about my chin (and looks good!). Both me and my sister notice nice volume whenever we even just trim our hair.
If you have dead ends, get rid of those for sure, that should help. I think layers would be nice. Maybe a small trim (if you're not into the thought of short hair) and long layers. For a long time, it's worked out for me and my sister.
Me and my sister (and you, it seems) have about the same curl type and it looks like about your face shape is close-ish to hers. What my sister has is boob-length hair (she's growing it out, btw) and layers (shortest at about her chin). She just got the tiniest trim last week and her volume is back! We both have thick hair and I really wouldn't recommend thinning. Your hair is pretty as it is, just needs some volume
I once went to this lady to get my hair cut and she messed it up by thinning (w/o my permission, I might add!) and it messed it up. That's just why I'm completely against it xD
Good luck! Hope I gave some kind of help