From the picture you look like a skinny guy *without* boobs. Maybe the light doesn't help, maybe it's the wrong angle, or maybe you are stretching but it doesn't really look like you have breasts. Definitely not an A cup from this picture.
Up to what point can you show off your body? Well, I am not sure what you are after. Breasts are not usually part of a male anatomy and while you will be socially accepted even with a D cup as long as you wear it with confidence, this doesn't mean that you'll be considered a "model boy".
Then, there are many types of beauty and I personally love the androgynous style so I find small breasts on a guy interesting, if well formed and feminine. But again, they are a feminine trait.
From what I see I think you can go on growing a bit more. Since the "filling" of the breasts comes later, you'll probably develop some conical shape first and that's where you should decide if you want to go ahead and have round ones or stop and work out until the conical shape is reabsorbed (or grow some muscles underneath and they will disappear).
When you get old there is a good chance that you'll have man boobs anyway. (And your GF won't have perky boobs forever too...). If you decide to go for the round shape, I have to say that most men that are on this site have better shaped breasts than women their age. You can also keep taking herbs at a maintenance dose to keep your skin elastic and use estrogen creams to "keep them up".
I would suggest you find a body type you'd like to get to, discuss it with your GF and then decide. Since you are young and skinny I could suggest you check out
https://www.reddit.com/r/traps/ (NSFW).
Good luck with your adventure and keep up posted!