If I have the gene for sickle cell disease, is it possible to not get the actual disease?

Yes. One copy of the beta-globin gene mutation causing sickle hemoglobin is called sickle trait--the other normal copy (most genes are paired) makes sufficient normal globin to prevent disease. If you as a person with sickle trait (carrier of sickle cell disease) marry someone with sickle trait, then you have a 25% chance to have a child with sickle cell disease with each pregnancy.
YEs. If you have one copy of the sickle cell gene then you have sickle cell trait and very likely you will have no symptoms perhaps just a mild anemia. If you have two copies of the sickle cell gene then you will have sickle cell disease so called, hemoglobin ss. There are some conditions that may make the signs and symptoms of hgbss much less severe like hereditary persistence of fetal hemoglobin.