Heart problem..and now strange symptoms?

about 12 years ago i had open heart surgery to fix quite a severe hole in my heart. I was left with a heart murmer, and the Dr said i would probably need medication for heart palpatations in the future, which i do occasionally have. Anyway, i'm 16 now and i've been experiencing some wierd symptoms, and i was wondering if anyone could help identify the problem? Basically i sweat too much for even a small amount of exercise such as a steady walk, and it's usually in my face, i look like i've been for a swim. My face also turns red and my cheeks start burning at the same time, it's not just a blush, they actually go scarlet and become quite uncomfortable. This also happens for no apparent reason when i'm just sat doing nothing. If I am actually doing any exercise my face tends to turn purple and the rest of my skin covers in pink splodges. They usually last for up to 20 minutes. Another problem is that I seem to turn cold really easily, especially my hands. They also turn pink with white splodges in the cold and swell up slightly and they''re quite painful. Anyway, i'm sorry to have made this so long, it's just that i really want at least a vague idea of what's happening. Thanks in advance.