When you say:
My internal hard drive is filled up all the way but none of my original footage is stored there
Can you be more specific please? How full?
Though your Project and most working files are on the external, there are still some files written to the C:\, and if one is using Windows Virtual Memory (especially if dynamically managed) located on C:\, you could well be running out of HDD space on C:\.
Also remember, when one fills an HDD to about 70% of capacity, its efficiency will diminish. The closer to capacity, the more the efficiency will diminish. At 100%, the chances of a catastrophic failure increases greatly.
13.9 GB free space is all i have left. i dont think anything is being stored on the external as i have just put it on a couple of days ago.
How many internal drives do you have?
only one. i really need some help with this i dont know what to do
You dont have enough hard drives in your system so your set up is less than ideal.
Basically you are out of "headroom" to process the footage and your system is telling you so.
The process needs the storage on the drives.
is there a way i could redirect everything to my external?
Maybe ..but you are likely to run into connection speed issues.
eg USB 2.0 connection is too slow for what you are doing.
You have simply run out of sace ("fast HDD space") due to the size of your finished programs and the shortage of HDDs.
More HDDS required or a major clean out of the ones you have.