What do you say to someone you haven't seen in 17 years?

I saw my father recently for the first time since I was 3. He showed up once between then and now (on my 10th birthday), but other than that I haven’t seen or spoken to him.
He asked the usual. How am I? How’s school? How’s my mom?
Would it have been ok to ask him where he went? Why he didn’t keep in touch with me?
It kind of hurt to see him. I felt like I was being left all over again. =[