Swapping antennas won't do you any good since it needs to be adjusted to your radio - the next antenna will probably give you the same results.
Since the radio you have does not have a built in SWR meter, you should consider buying one to test with. Radio Shack has them and they are not expensive. Typically you check your SWR on channels 20, 1, 40. Also, tune it where you have open space around you - it makes a difference.
The antenna you have is adjustable, remove the top cap and you'll see a set screw, you can loosen the set ring and adjust the screw in and out depending on your SWR readings.
This will help you dial in your antenna:
http://www.firestik.com/Tech_Docs/Setting_SWR.htm