1994 Pontiac Grand Am sticks in gear

The problem in the beginning was it would periodicly stick in first gear untill you reached 35 mph then would finally shift but now the problem is when im slowing down it struggles coming out of say 3rd or 4th gear and it bog's down and acts like its going to stall. Then I figured out that I could manually shift it to low 2 and that would stop it from stalling. I would like to add that the problem only happens after its warmed up and ive been driving it lets say 10 or 15 minutes. And sometimes I would be putting along 25 mph in 2nd gear and it would down shift hard to 1st gear, its the only car I have , . Please help