Yes, if you wash repeatedly with Tecnu Extreme it may be drying your skin. Discontinue washing with Tecnu Extreme and apply a moisturizing lotion to the area. Petroleum jelly (Vaseline) may be good to put on it as well.
If you have been washing with Tecnu Extreme, the urushiol should be gone and therefore your rash should not spread anymore. If you find your rash does spread, then you are coming in contact with the poison ivy or oak plant's oil (urushiol) again. Urushiol can stay on surfaces such as tools, clothing, pets fur, etc. for a very long time. You may need to decontaminate those items as well.