Help with new guinea pig...Do they ever get adjusted to their new home and owner?

I bought a guinea pig about 5 days ago, and am still having a hard time with him getting adjusted. I try to get him out everyday and pet and play with him but when I do, he acts really petrified and trys to hide and wont let me cuddle him. He makes little grunting noises that makes me think he is hurting or something. I know they are supposed to be very friendly and playful animals, but I am worried he wont ever let me play with him. How long does it usually take these animals to adjust and ger comfortable? Any suggestions on how I could make it easier for him and what I could do to make him less frightened?