Repeat situations that make you blush. And go beyond those. Me: I did blush like a tomato when I have been kissed in public. But I loved that and repeated it as often as possible. Then I added a bit of hugging and bottom stroking to it. Which made me feel awkward a bit but I loved that too. After a while I stopped the bottom clapping and just indulged in kissing. Then that was not making me blush any more. Don't know if that works for you. Boys are different. Kissing boys in public seems to be more of a problem than girls usually depending on environment, but you get the principle?