Infinite uploading

Hello forum,

Using my arduino due, I just noticed that when I try to upload my sketch, I either get an infinite upload (never completes) or I get an error code. Either way, reinstalling drivers etc. etc. doesn't work and I'm starting to fear this is a problem with my board. I will include both error codes, as the infinite upload also displays some error codes.

this is the infinite uploading code:
    at cc.arduino.packages.uploaders.SerialUploader.uploadUsingPreferences(
    at cc.arduino.UploaderUtils.upload(
Caused by: Fout bij het aanspreken van de seriƫle poort "COM5"
    at cc.arduino.packages.uploaders.SerialUploader.uploadUsingPreferences(
    ... 6 more
Caused by: jssc.SerialPortException: Port name - COM5; Method name - openPort(); Exception type - Port not found.
    at jssc.SerialPort.openPort(
    ... 7 more

this is the one I get for larger codes:

C:\Users\gillian\AppData\Local\Temp\build04ab5278adf08dec5c4a77179f8d33ba.tmp/core\core.a(main.cpp.o): In function `main':

C:\Users\gillian\AppData\Local\Arduino15\packages\arduino\hardware\sam\1.6.9\cores\arduino/main.cpp:61: undefined reference to `loop'

collect2.exe: error: ld returned 1 exit status

exit status 1
Fout bij het compileren van board Arduino Due (Programming Port)

Hope someone can help me!

Regards, Gillian