Why is it that whenever I try to work on my computer, I fall asleep.

Don’t sit in front of the computer. Easy.

I don’t know but as @elbanditoroso suggests, perhaps get a standing desk.

You may be multitasking way too much on top of not getting quality sleep at night. Turn off the TV when you are doing other tasks and go to bed earlier and read without the TV on. You sound like you need more sleep.

Put the computer on a higher platform, like others here suggest. Or on a treadmill.

Maybe you have a big sleep deficit. How many hours a night do you sleep?

You might have mild narcolepsy.