Anyone else had knee pain from working out a lot?

When I first started to lose weight, I started by walking, a few months into walking I noticed that my right knee would hurt sometimes if I put too much pressure on it. Fast forward to now, and the pain has increased, it's difficult for me to run. When I stepped off the side walk today and placed my right leg first, I had to stop in my tracks because it hurt too much.

I'm going to the doctor tomorrow but was wondering if someone had similar pain before from exercising and how they fixed the problem. Thank you.
Anyone else had knee pain from working out a lot?
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