Severe Knee Crackling With Intense Pain

Everything i've read online says that knee crackling (sounds like you're crushing a huge bag of leaves) is called crepitus and is totally insignificant/benign.

I have had the crackling for a few years now (i'm 34) but lately (for the last year) the crackling is accompanied by intense pain. I can't go up and down the stairs without my right knee aching. The knee has become noticeably weaker since the pain started as well. I exercise daily (30 minutes of aerobics and 30 minutes of weight training for upper body) and I can't perform the simplest of lunges or squats without major crackling and pain.
Because of early menopause i've put on 8 pounds in the last year so my husband insists it's just added stress from weight gain (i'm 5'2 and weigh 122 pounds..Hardly overweight)..I have four kids that keep me active as well..

What is wrong with me? Do I need to see a specific doctor? Will this require some sort of surgery? I'm too young and active to lose mobility in my knee..And if I stop exercising because of it, that'll have disastrous effects too..

Any advice??