Fed up with the static..

Please bear with me as I dont know much about them just what they can do for me..
Having trouble with the cb in the truck i use at work which is a cobra 18wx (I realize it's not the greatest) I would say about 75% of the time it just has horrible static. Today I started out and it wasn't bad but after about 15-20 miles it started to pick up more and more to the pt where I had only a slither of a turn left on the squelch. Even then it would still occasionally break through and was like this the rest of the day, basically it was useless.
Other issues I commonly have are some days:
It will sometimes pick up signals from way down south(im in ny) yet I wont be able to get a signal from 500ft in front me.
The static on occasion will also kick up when the left signal blinks or for a split second right after I disengage the jake each time.
When I go to talk it will be fine for 2-3 secs then it just goes to an ear drum piercing squeal.
All this said it's if its has these issues one day, it's entirely possible that it will be fine the next day..

We have another truck with the same exact radio except he has dual mirror mounted antennas and his is perfectly clean. I only have one mirror antenna(similar to this one.. http://www.cbradiosplus.com/product_p/1516.htm ) I see it has a factory antenna setup but for whatever reason that cable and mount isn't being used.

Any thoughts, does this all seem like just an antenna related issue?
We don't really need radios as we just run local to various grain elevators and field to field, so trying to get the bosses to ante up for better radio or antennas is unlikely. But like many, it's nice to hear up coming traffic issues or say hey if I pass a buddy..
Thanks.

 

Thanks for the tips. I haven't been in the truck since I posted but will be tomorrow so will the give the antenna disconnect a try. . I can't picture the antenna grounding setup off the top of my head so I'll try and give that a look to.
As for the ear piercing squeal, I don't have any sort of talkback feature. Like I mentioned it's just a simple cobra with a squelch and channel knob and a sound tracker button. The squeal was so bad wednesday, that the scale house told me to stop and just walk in with my info..

 

I switched mics quite a while ago wondering if it wasn't grounding or something when clipped (this was to try and eliminate the static issue)
It wasn't until about a month and half ago when I just happened to be in a different truck one morning and another guy keyed up in this truck that I heard the god awful squealing. It transmits for about 2 secs ok, then squeals.
Like I mentioned in my original post, I'll have all these issues one day but then the next day it'll be fine. No static and I can talk without it sounding like marbles in my mouth or squealing..

I goggled some info earlier that discussed making sure the cable isn't pinched anywhere. When they installed it, they routed the cable through the wing window so perhaps it's been pinched? Truck is a 379 pete if that makes any difference.

 

Just uses a stock cobra mic, nothing fancy.. I spent some time messing with it over the week or so and THINK i may have it figured out...
Originally it was mounted up on a bolt on mount that was located on the first section of the mirror arm (between the door and first bolt). Took it apart there and found it packed full of white rust.
So I moved the antenna over to where the old factory cable ran to into a hole in the bracket behind the passenger mirror. Wasn't til yesterday I got some time to take it all apart and I cleaned everything up and sprayed it down with some silicone spray and today it was much better.. Nice and clear with the only static being around a few high power power lines that always set it off for a few seconds. Heard 1 guy from 4 miles away as well!
I also noticed today that it ran with only 1 sometimes 2 of the leds lit up on the screen. In the past it would have 3 or 4 lit up.
I suppose the real test will be tomorrow. I've been on a different route the last week or so, but tmw I'll be back on the route I was on when I originally posted my frustration so will see... Thanks so far for the help!