Advice on Knee Pain

Just over 2 weeks ago I developed severe pains in both my knees, likely from having failed to properly adjust the saddle height on an stationary bike. The pain only came about the next morning, but it was so bad I could barely bend my legs; an x-ray showed that nothing was broken and no ligaments were damaged, only some fluid around the kneecap.

After continuing to rest and take painkillers but only seeing a slight improvement over 2 weeks, I went to see the doctor who diagnosed it as chondromalacia patella (cartillage damage beneath the kneecap.) I’ve not exercised these past 2 weeks, resting as much as possible, but I still find myself unable to walk 100 metres before I notice real discomfort and increasing pain; anything I’ve read online says that the condition is noticeable during sporting activities, but I can’t find anything that mentions cases where it’s so debilitating that even just walking is difficult.

Likewise, stairs cause problems, as does bearing additional weight. Is it possilbe I was misdiagnosed and it’s a more serious condition? Any advice as to what I should do? Appreciate any advice whatsoever, as this is affecting my day-to-day life, let alone preventing me from exercising.