Chances are very high that your hard drive is failing. Make a backup NOW! Then proceed with the following test options:
Use
Onyx to check the SMART status of your drive. If the drive doesn't pass, then critical drive failure is imminent.
If the drive passes, it's NOT safe to assume that it's OK. Most SMART reporting tools rely on the drive's own assessment of its health, and the drive manufacturers are highly incentivized to wait until the last minute for a drive to be declared dying. A much better SMART reporting tool is
SMART Utility. It does a more thorough analysis of the SMART data and can provide an earlier warning of a failing drive than other SMART tools. SU isn't free, but it is cheap and has a free trial, so take advantage of that.
When you try SMART Utility, select your drive on the left; on the right, select
More Info at the bottom in the Tests section. In the pop-up, change from Short to Long, then run it.
If that passes, then it's highly unlikely your drive is failing. You can be absolutely certain if you like with
TechTool Pro, which can do a surface scan to check for bad blocks. It's not cheap, nor is there a free trial. But it is the best tool of its class, IMO.
Report back with your findings. If the drive checks out, we can troubleshoot further.