3000GT problems

I have a 94 3000gt non turbo. The runs great, except 2 things. There is a white smoke coming from the exhaust, just enough to see, and doesnt go away from warming up the car (catalytic converter) there is also apparently an oil leak. I have to add oil about once a week - 2 weeks. And with the oil leaking the oil pressure gauge goes down, but never over heats, and im not leaking/ losing coolant. Any idea what could be the problem?