Problem with my knee. Don’t know what is wrong!

Patient: Problem with my knee. Don’t know what is wrong!I am 26, and I have not had any knee injuries. I am 5’10, 160, no serious illnesses other than borderline high blood pressure, no surgeries or major injuries related to my legs (although, lots of ankle sprains when I was younger), and I have been physically active through elementary, middle, and high school.It occurred after doing lots of things with friends in one day, like laser tag, running around and doing other things like basketball, which is not typical of my ordinary routine the last couple years, because I am sitting down all day on my computer.I don’t remember hitting my knee or hurting it. I only remember towards the end of the day my knee started hurting so bad I couldn’t walk or even stand up.So basically, here is the problem:If I walk around, even at a casual pace, for more than maybe a mile or so, then my knee starts to hurt so bad I can’t walk. As long as I just stay off it, the next morning I wake up and am fine. But if I do any kind of activity like walking around for more than a mile or so, then the same thing happens.- The pain is on the front-outside portion of my knee.- It does not hurt to the touch or any pressure when it hasn’t been hurting.- Only on really hard pressing WHEN it is already aggravated, can it hurt at all. It is not painful to the touch.- WHEN it is aggravated, it only hurts when walking or standing on the knee. If sitting or putting weight on other knee, there is no pain at all.- If I stay off it for only a night, then by the next morning all is well as if there was nothing wrong- WHEN it is aggravated, it hurts even worse to try to walk downhill and I feel like I am about to fall over and collapse.- WHEN it is aggravated and I am trying to walk on it, it is a severe, sharp pain, but not on the skin, on the outside-middle of my knee.- WHEN it is aggravated, staying off it only a couple minutes is enough to diminish the symptoms slightly. However, it isn’t until the next day of staying off it, that the symptoms go away completely.- WHEN it is aggravated, it is not swollen as far as I can see, or tender to touch, or bruised. It just looks normal, and feels normal unless I’m trying to walk or stand on it.WHAT IS WRONG???!!!I work from home as a web designer, so I do not get out much, so I have only had this happen a few times in the last couple months because I spend all my time at home.I want to see a doctor but I do not have health insurance since I only make enough to get by. I AM FORTUNATE because otherwise this problem would put me out of work!!