What is happening is akin to "Pavlov's Dog" (conditioning) - you know the story of the experiment where Pavlov would ring a bell, then feed the dog... then after only the bell would ring the dog would start to salivate because he was conditioned to getting food after hearing the bell? Well, logically you KNOW you are OK, but after being worried about the blood for so long, now when you SEE it your anxiety rev's up because you became "conditioned" to that feeling and fear when you saw the blood. No matter how many specialists tell you that you are OK your inner self can't believe it (although your logical self can)
I had a mucus retention cyst on my tonsil and my throat on that side would get a funny burn feeling into my ear about once a day for a few seconds. I was convinced it was the cyst and that it really WASN'T a mucus retention cyst, so even after the doc said what it was and it was nothing, every time it burned I freaked out. Well that cyst has been gone since December and I STILL get that funny burn and do you know I still get an anxiety reaction when it happens? I KNOW the cyst isn't there, but I immediately think of it and my subconscious takes over.