My COM port is not showing up anymore

Hi, I have been using Arduino/Genuino Uno on my lap top for about a month now and its been working fine until today. (Windows 7 Professional)

The first time I used the program I had to select tools > Port: COM ## and select a port. At first there was only COM3, but after a few minutes another option appeared. It had a really long name but I'm pretty sure it said "COM4" at the very beginning. From then on every time I used the arduino I used the same usb input and it always connected to the proper port automatically. Today at school in the middle of my lab, after uploading programs to the arduino multiple times, it all of a sudden showed error messages saying cannot connect a bunch of times in orange text. I checked the tools > port COM# and the only port available was COM 3

I switched to the next usb port over after a few times of trying to upload my program and it started working again for about 20 minutes. It then stopped being able to upload programs again and hasnt worked since. SO WEIRD!

Ive tried rebooting the program, my computer, troubleshooting on google and on the arduino site and reinstalling the program.

Easy things to try are swap out the USB cable.
Try it on another computer.

After that then you need probably to tell us which IDE and boards version are you using ?

Were you on your own computer in the lab or a school computer ?

Is it a real Arduino or a clone ?

And anything else you think may help people to help you.

Oh and go back to the top of the troubleshooting forum and read the posts from the top down !