2003 Chevrolet Monte Carlo transmission fluid leak

Transmission fluid is leaking from my car around the transmission cooler pipe near the radiator. I removed the connector and went to purchase another one but the only store open was out of stock. So, I replaced the connector and added more transmission fluid hoping this would get me to the auto parts store in the morning. Can I have tightened the nut on the connector too tight? The transmission fluid was dripping out very rapidly around the connector after I replaced it. (So I kept tightening it until it slowed down but never stopped) Anyway, this morning I cannot get the connector off of the pipe. I loosened it without a problem, took the spring off easily but I cannot get the connector off the end of the pipe? What is wrong? Please help me