I am not sure if you saw a ortho or sports med doc, but I would see someone who knows knees well first. The treatments for things like patellar tendinosis or patellofemoral pain/chondromalacia are varied, but most of them involve some form of very committed physical therapy. And since the therapy is different for the different diagnoses, you want to make sure you have the right diagnosis before you start (otherwise you could spend months or years doing pointless exercises).

I treat people with these problems on a daily basis. Get the right diagnosis first. If you feel like you have it, then you are going to have to commit to a significant PT program. This will likely involve more than a couple of home exercises and it wouldn't be a bad idea to see a physical therapist, depending on the problem. There are braces that can be helpful, but there are different braces for the different conditions. I do injections of prolotherapy for patellar tendinosis but generally injections don't work for chondromalacia. Sometimes surgery is an option depending on the condition.