I am having an incredibly hard time shifting. I basically have to force it into gear. My car won't go into reverse unless I turn the car off, put it in reverse, turn the car on and then reverse. 1st gear I have to force into gear, same with second. The other gears are hard but reasonably easy to shift into. This only start after I had someone do a coolant flush and diagnostic on my car but unfortunately it was a mechanic out of his house and not at a shop. Any ideas? I had the clutch replaced 3 years ago and I'm pretty easy on it. This is becoming a safety issue as sometimes I can't get my car into first at stop signs or lights.

Let me know if any other information is needed.