I was 14 when I had my son and I am looking for him. I emailed the adoption agency and hoping I get a response. He was born in Sioux City, Iowa at St. Lukes Hospital and I am worried he does not want to locate me. Any ideas?

There are state birth records too. That's where you can find out if he is on file for wanting contact too. The odds are probably pretty low while he's still in his 20s, but you can go on file as wanting contact with him, wait, maybe try Facebook, as well as many sites online that match people by such things as birthdate.

https://www.askmehelpdesk.com/adoption/looking-birthparents-children-given-adoption-401680.html

In the above link, I give the best initial strategy for starting your search. Going through reunion websites is probably the BEST way to do it, since then you will know if he WANTS contact with you.

First the child may or may not even know they are adopted, some families prefer not to tell the child, want to wait till latter but then never find the right time.
So first you have to assume the child even knows they are adopted.
Then you have to assume they may or may not ever want to contact any of the bio parents, Many adopted children have no desire to meet or contact birth parents, others go to counseling to get past any desire to meet.