Well... for what it's worth I could tell it was the same rider in all the photos (at least the ones showing your face! I'll trust you on the two flat photos you posted second!).
Your horse is beautiful, and he looks like he is a very talented eventer! You also look beautiful, and you are a talented rider. The one thing I notice is that you don't have a lot of consistency--in some photos, you have a really nice, secure position. In some others, you're jumping ahead way out of the saddle or you lost your base of support and your leg is swinging back. I struggle with this problem too though, so I definitely understand! I think with time and practice you'll get better. Strengthening your legs, both in and out of the saddle, will also help with this.
If I were you (and I really wish I had your position in some of these photos!), I would really work on keeping your leg from swinging behind. It will really help you advance and keep you secure, which is particularly important in cross country. Even though you don't have an automatic release, it almost looks like you have the beginning of it in some of these photos. Once you feel more secure in the saddle and are more consistently jumping with your leg beneath you, I think you're absolutely at a level where you should begin practicing that. In the meantime, make sure you're giving enough of a crest release. A few of these look like you're pulling on your horse's mouth a little bit. Again, this is just a consistency thing.
Best of luck to you! For what it's worth, I don't think you need to lose weight. Don't worry about that one bit! Just enjoy your horse, always continue to work on your riding (we are never too good to improve!), and have fun doing it.