I suggest that if it's a big problem for you, you should seek a psychologist. We often discuss being a sissy on this site, and sometimes our advise or support is unrealistic. What you're asking from your gf is a lot and puts a lot on her. If it's not her thing, and I would guess it's not for most girls, you're both going to have different and opposing desires.
As for your question, "am I a sissy", it certainly sounds like you want to live that lifestyle. At age 19 you are going to have acceptance problems because you've probably been raised to see yourself as a male in all the typical, socially accepted norms. As an AB/DL person from an early age, I had lots of problems accepting that part of my personality. I grew up on the Jersey Shore and even had friends whose parents were in the Mafia. We were expected to be tough and getting into fights was part of my life. Justifying that with wanting to wear and use diapers was a big problem for me.
As I grew older however, I began to accept who I was and I accepted the fact that I was many things, not just some kid who had to be tough. I also needed those desires satiated by wearing diapers to be appeased. Acceptance is liberation but moderation can enable a more healthy life. There's a time and place for all things and we have to live in a vanilla, muggle world. Only you can decide how far you want or need to take your sissy life.
When I went to college, I threw caution to the wind after I was dumped by my serious girlfriend and took up with a guy. Our relationship lasted all through college, so yeah, I sucked my share of cock, but I usually was a bottom. It can be done, but there were a number of prices to be paid with my last year seeing me as a patient in a mental facility, so be careful. The road less taken can lead one to a very different destination.
