Ok, this is my advice, I'm not doctor or anything, so take this as you will...
Your aches will always be there unless you're pretty fortunate. My knee slighty aches as well right now. In fact, the last time I was on a plane, the boring pain was so intense that is was one of the worst feelings I've ever had in my life.
Mind you that was a few months back at 21 years of age, and my surgery dates all the way back to when I was 6. What I do when the pain is intense is take a HOT bath. Thankfully it doesn't happen THAT often. I'm just warning you that you may want to get used to dealing with it.
As far as the sharp pain, that doesn't sound right. Even though your doctor tells you you're ok, you have to be the judge of your own body. In fact, many doctors these days just flat out don't know what they're doing. In fact when I was on crutches awhile after my surgery, I was given the go ahead to be off of them and walk on my own. Needless to say a second doctor eventually spazed out and said there was no way I should've been off crutches that soon and then put me back on them.
1) You'll probably always have pain of somesort. You just have to determine which pain is acceptable and which pain is out of the ordinary. You have to be your own judge and fluff off the small stuff.
2) Not all doctors know what they're doing. Getting second and sometimes even third opinions is very beneficial.