@Cupcake15 - I think that that is the hardest part of medicine because you have to do a lot of research and even though you have a lot of information, you still may not know what the patient has which has to be really disheartening.
I remember watching a television program that dealt with this sort of thing. The patients all had progressively worsening conditions, but the doctors continually misdiagnosed the problems and only after the patients sought renowned specialists did they get an accurate medical differential diagnosis.
There was one case where a little girl would get bruised just by playing on the floor and one day she was bleeding uncontrollably.
It was eventually discovered that the little girl had a very rare disease that did not allow her blood to clot correctly which is why with the littlest scratch she would make her bleed. The doctors were able to give the little girl the right medication and she finally received some relief from the disorder which was also a big relief for her family as well.