Car not going into any gear

I have the SE model.
I am not able to put the car into any gear at all. When I try to put it into gear the car does act as if it wants to move forward but nothing happens. I did have grinding noises when I put in third gear or reverse. When the car is off all gears shift smooth with no problems. Only when the car is on it will not go into any gear.
Any suggestions on what it may be or a fix?
*Note* When I changed the slave and master cylinder it started shifting into gear for a while then eventually went back out to not shifting into gear at all. Now it just will not shift into any gear at all no matter what I do. Please let me know what you may think the problem is. I lost my job because of this problem.

Things that I have done to the car:
Changed the clutch and flywheel.
fill with new gear oil.
bleed clutch several times.
Changed master cylinder.
Changed slave cylinder.

By the way the car only has 90,000 miles on it.