2002 Pontiac Grand Prix Oil leak and shifting hard

My first problem is the most severe. It started out leaking a little bit of oil, then within 2 weeks, it was a deluge. When you put the oil in, it comes right back out from about the midpoint of the engine. I checked the oil pan and the problem is not there. I am wondering what it could be, a gasket or something easy, or more severe like a cracked piston head. It looks clear, not foamy, so I am pretty sure it is not mixing with any antifreeze. On to my second problem. When the car has been driving for a while and the engine warms up, the transmission starts to shift really hard, sometimes physically jolting the car in the first 2-3 gears. Sometimes when you turn the engine off for a minute, the problem stops, other time it does not. Thank you for oyur help!