Guy with an embarrassing sex problem?

I am 37 and my girl is 23, she is incredibly beautiful! (who knows what she sees in me) And she's the sweetest. She decided she was ready to have sex with me a few weeks ago, but it didn't exactly go to plan. I started taking off her clothes, and when she was just in her underwear, I felt myself getting hard. She unbuckles my belt and we got my trousers off, and then I started on her bra. Well as soon as I'd unclipped her bra and her breasts fell out I *came* immediately......... That has never ever happened to me before, I was just taken aback by her beauty. After I had recovered, we started again and while we still on foreplay it happened again. We decided to leave it for the night and come back to it later, because it was obviously not the right time! She was actually very sweet about it. But I'm absolutely scared to death about it happening again because I'm embarrassed about this. How can I stop myself from coming, without actually avoiding looking at her face or body of course! Don't tell me to get a less hot girlfriend because she's amazing - I mean she made me come twice just by looking at her, she is amazing. But I need to be able to satisfy her and not just myself, or she's gonna leave. Thanks guys, appreciate the help. Please don't be too harsh... ha