My "Age Gap"
I wouldn't say that your age difference in years is very large. I'm 12 years younger than my wife.
It Depends On the 19 Year Old
The real issue here is maturity. As a father, I would have no problem with my 15 year old daughter dating a 19 year old who I thought was together, whose motives were genuine, and who wasn't just looking for a quick sexual experience and then would disappear. However, also as a father, I must say that I would feel really terrible if she was dating ANYONE behind my back.
Have you talked this over with your parents?
Also, if you're not ready to "get physical" be extra careful. Not many 19 year olds are interested in a no-touching relationship with a member of the opposite sex. So, what is it you really want? What does he really want?
Age Difference Shouldn't Be the "Turn-On"
Finally, don't let the age difference be the main turn-on. You guys should like each other IN SPITE of the age difference not BECAUSE OF the age difference. Get it? It's a turn-on to be going out with the older guy. It's a turn-on to be going out with the innocent young girl. Get over it fast! That's how unwanted pregnancies happen. That's how real hurt happens.