My knee feels like a tight rubber band. i can't squat down or put a lot of pressure on my right knee. what could it be?

Fluid buildup: You may have fluid (an "effusion") around your knee. This can be from wear-and-tear or a minor injury. First, don't squat! That puts a lot of pressure on your knees. Second, ice your knee four times a day (a bag of frozen peas or corn works well!). Rest that leg and elevate it. Take ibuprofen 2-3x a day if your doctor is OK with that. It should be better in a week or less. If not, go in!