2001 Saturn SC2 Humming noises and odd RPMs

For the past week, my car has been making this odd high-pitched humming noise when it reaches highway speeds. It sounds as if I am still in 3rd or 4th gear revving the engine at 4 or 5 thousand rpms. The problem is that I'm in 5th gear with somewhere between 2 and 3 thousand rpms. Just yesterday, I noticed that my RPMs were off from what they usually are, especially when slowing down. When approaching a stop light, the RPMs usually drop down under 1000 normally after I take it out of gear. However now it will stay around 1500 until about 5 seconds after I've completely stopped (again, in neutral).

A couple other side notes that may be useful:

The humming noise happens even in neutral, and I've only confirmed the noise while in 5th gear.

The 'hum' sounds like it's separate from the normal engine sounds. I can hear the engine running like usual, but the hum is also there, over-lapping it.

Also within the last day, I've noticed that when going about 35 mph in 5th gear, the car seems to drive itself. I barely have to touch the gas to keep it going that speed. This is different then in the past.


Thanks in advance for any help. Let me know if you need more information.