Computer is really slow, i get the beach ball for a couple of minutes, and when I right click on something in the dock it freezes and I cannot click anything else.

So this started 3 days ago, I was doing some work and noticed it was running very slow. I restarted the computer and it got worse. It's gotten to the point where it freezes or beach balls for a certain amount of time, usually a few minutes, and beach balls again. When I right click on the dock to quit or force quit something, it the icon dims black and and the dock freezes while it is still up, I cannot click on anything else and I am able to move the mouse. Browsers and programs do not open. I have gone into the activity monitor and everything checks out. I still have plenty of memory, the memory pressure is fine. The System and User Percentage is also fine. When I put it into sleep mode by closing the monitor, and reopen it, I get a black screen and a visible mouse. Any suggestions to fix this?