Hemangiomas are a kind of a strange phenomenom that occur from time to time in women mostly. They are abnormal accumulations of blood vessels that can occur virtually anywhere in the body. Why they occur is still unclear but some researchers believe estrogen plays a role (hence the increased occurrence in women). I can see that it would be unsettling to have them show up again and again over time but the good news is that they're usually benign and usually disappear - this is presumably why none of your three doctors were concerned about them.
Here's some information on liver hemangioma's (http://www.medicinenet.com/hepatic_hemangioma/article.htm)