Finger Nail Splinter Haemorrages

Hi, I am 41 (male), average weight and fitness, and have had splinter haemorrages on my thumb nails what must be for several years now. After worrying myself to death by looking up possible causes on the internet, alot of the medical websites said this may be a sign of some kind of heart problem (bacteria of the heart valves).
After seeing my doctor a couple of times about it over the last two years, he literally told me off for looking it up on the net and said there was nothing to worry about. He even said if it was to do with my heart, then why wasn't it on all of my fingers. Well over the last six months, they have started to spread to my other fingers, and occasionally on my big toes. I seem to be getting out of breath quite easily now, just walking up a small flight of stairs.
Could anyone give me any further information and should I be worried???
Many thanks.