help!!! abnormal transmisson leak

okay i am a girl...so i don't know much about cars. I have a 1999 mazda 626. The check engine light keeps on going on and when i bring it to get it checked the computer is saying it is my catilac converter, i guess nothing serious? but then i seem to always be leaking tranmission fluid, i brought it into my machanic and he said it was a gasket he fixed it then it was leaking again. I brought it back to him and he said the cold whether makes the gasket leak. So he tightened it again and guess what its leaking again!!! i find this to be a little crazy!! does ne one know whats going on with it?

where is it leaking from? could you take a pic?