Your post has already received some insightful comments and advice but one thing I wished to offer based on the title of your post is this. You should never doubt that you are a submissive based on the fact that you don't choose to submit to every dominant personality, either in or out of the lifestyle. It is always the choice of a submissive who they submit to. It is meaningful and feels right to submit to some but not to others. Submissives are not door mats that are required to submit to every person who claims the title of dominant. Some may disagree with me, but our submission is not taken from us, it is a gift we bestow by choice on those with whom we build a bond of trust. We submit from a position of strength not weakness.

One final thing is that you need not feel submissive all of the time, every moment to be a submisssive. There are times when I don't feel submissive at all. During intimacy with a woman, in a purely vanilla sexual experience I can comfortably fill the dominant role which I think is simply natural because I'm male. Yet that doesn't give me cause to doubt that I am submissive as far as the lifestyle goes because I know how meaninful and fulfilling I find that role with the right dominant female. Within the lifestyle, I respect all dominants but I don't submit to all. We are all simply one of two sides of the same coin. Without a dominant a submissive has no opportunity to submit and without a submissive, a dominant has no one to exert authority over. That is why it is called a power exchange. It is purely voluntary on the part of the submissive to choose to whom and to what degree to engage in that transfer of power.