How to get over this crazy fear of blood?

I feel like I have a fear of blood, but it's very confusing and I don't know if it is a phobia or not. Whenever I read about blood or learn about it in school, I get this awful sensation and it feel like I have to get out of that situation no matter what. For example, I had to research mosquitoes for a biology ignment and when I was reading about the blood digestion I couldn't handle it. Also, when we were learning about blood types I got really pale and felt like I had to get out of there. NOW, here's the weird part: When I am actually in contact with blood, I don't have any fear at all. I can easily patch up my wounds. I volunteer at a hospital and I carry around blood for transport all the time. When I gave blood for a blood test on the other hand, I can say it was one of the worst experiences of my life. I want to study to become a doctor, but I feel like this is really going to get in the way. Also, on TV when people like cut their hand with a knife to do a "blood pact" or stuff like that, I can't stand it. I was wondering if this is normal or what, and if there is a way to get over it? thanks so much