1995 Toyota Camry trans problem

I have a problem with my trany when the car is going it does not make the shift from 1st to 2nd gear, it only makes it if you let go on the gas pedal otherwise it stays on 1st gear. My other ptoblem is that whe it finaly shifts to 2nd gear you press the gas pedal to accelerate and looses the shift and goes back to 1st I replace the oil filter and oil but it did not help. Hope you can help me thank you.