I'm not sure about the stabbing pains, but you can have varying colors of discharge for at least 6 weeks after delivery. When in doubt, always call your doctors office. You should at least be able to talk to a nurse to determine whether or not you should come in.
My goodness three weeks? Wow I was still bleeding like crazy until 6 weeks and then it stopped all the sudden (they checked and nothing was wrong I was just bleeding.) I also had stitches so I had some "sore" pain down there until around 3 or 4 weeks, but I didn't feel comfortable having sex until 6 or 7 weeks. That's just me, but if your worried i would call your doc to be safe (I had my doc on speed dial lol)