You might just be a little confused trying to find your place. But in general, if you have to ask "am I a sub?" then probably not. An experienced sub would say that they really enjoy being a sub and making their Dom/Domme happy. It's a natural feeling for them.
The decision of whether you are a sub or not can only be answered by you. The depth of submission is to be decided between you and your Dom/Domme. I have always said... talk - talk - talk, and then talk some more. It is the only way to make things work.