I don't see it an issue about phone sex between two consenting adults.

I'm sorry that school counselor crossed boundaries. If he wanted a relationship with you, he should have referred your son to another counselor. Could he not control himself long enough to make sure your son's needs were met first? No. That counselor is dangerous around kids because he puts his own sex needs over maintaining healthy therapeutic relationships. That counselor was more preoccupied about himself than helping your son. I'm sorry. Why would that perv want to see your son get well? As long as your son was in need of therapy, the more time that counselor had to take advantage of you. I'm sorry.

Be angry at that school counselor, not yourself. You were vulnerable and asking for help and that school counselor violated you.