I am having problems getting my Phantom 4 to fly further than three-quarters of a mile away from me. This is been an ongoing problem since I have owned the Drone. I live in the state of Virginia and there are lots of trees could this be causing the problem?

You will find many threads about this issue

Try reducing the quality to 4 and choose a custom channel instead of Auto.

Although Auto is the recommended setting, try a custom channel to see if it works better.
Choose a channel which does not have red bars in each area you fly.

Also, what device do you use?  and what is the dji go app version?
(2.8.1 was the last good one, otherwise, you should be using the latest; 2.8.2 was very bad)

Trees wouldn't interfere with your signal unless the tree is directly between you and the drone.  Can you find an Android device and try again? Also, try fly somewhere in open field with little electronics interference(wifi, power lines, etc)