I had to have 4 units of blood 20 years ago so shouldnt doctor check for hepatitis and hiv?

Maybe. Testing for HIV started 1985-87. Testing blood supply for hep b started about 1972. Testing hep c started in 1992. Arguably you received your blood transfusions after the test dates (or not). Any other risk factors, e.g. Men having sex with men, tattoos (if at all not sterile needle and fresh sterile ink), IV or nasal drug use, multiple sex partners warrant test. Cdc sugg test born 1945-65.
Yes. Though the blood you received may have been screened, you are not 100% sure so I would check you if you were my patient.