To add to the above advice I think you should also work on your eyes
There's different expressions you can do with them, even "smiling" with them without smiling with your lips. Maybe practicing in front of the mirror? Or try to mimic the expressions of other models from magazines or any that inspire you, try to do the same facial expression and take a picture of yourself or just in front of the mirror. That could give you a lot of practice and a way to find what expressions are flattering for you in front of the camera. You're very lovely, I'm sure with practice and time you'll be able to get your portfolio to a higher level!