I had a bad case like that when I was 12. Ugh - bad memories! What worked for me is practically impossible to do. I did not scratch for 3 days or nights. That meant I was awake for 72 hours fighting the itch. Iit was summer, so I was able to wear as little clothes as possible to be 'decent' to reduce rubbing on the rash. I was miserable and no doubt I made everyone around me miserable. Gotta share the pain!
That, calamine lotion, corn starch baths and time cured me. I have been extremely careful not to get poison ivy again.
Good luck to you.