Samantha,
Really interesting question. I remember being a kid (around 12), and always saying and feeling that I was about 30-35. When I finally reached that age, it felt the same as I did when I was a kid. I am almost 40 now, and I still feel 30-35. Maybe I will always feel like that! LOL!
So my answer would be about 35 for no other reason than that has been my "feeling" age my whole life. I really wonder why? It seems like such an odd thing. I have never heard anyone else share a similar thing.