Please knees don't fail me now

Well its been about 3 weeks since I started training for the 5k in August and I couldn't be more disappointed at myself. I have injured my knee somehow. I have a doctors appointment next Tuesday in hopes to figure it out. Last Saturday I went to the Endurance store, had a foot strike analysis done, bought a really good pair of shoes and thought maybe it would help. Well Sunday I got up and went running with my running partner and we ended up doing over 4 miles. Monday I got up and tried to do my tae bo but my knee was so sore I could only get through about 25 minutes, my average is 45 to an hour, then later that night I went for a quick run to see if a knee brace would help, I got about 1/3 mile and had to stop. Tylenol, Ibuprofen, Aleve, and Excedrin work a bit but not enough to muscle through it. I am not just training for the 5k but also trying to get my butt back into shape. Its been harder this time around. With Jade it fell off rather easily with little efforts but with Ella, my goodness I feel like I am killing myself. Tae Bo at 5am, running at night, and bicycling on the weekends is not working like I want it to. I am also really watching what I eat, counting calories, monitoring the fats and have virtually eliminated the sweets. I am not perfect at it, I slip up. I started tae bo about 6 weeks ago and with the extra 3 weeks of running I have only dropped 11 pounds. I feel like it should be more by now but maybe I am just setting my standards too high. Sluggish thyroid maybe? Sad as it is to say I am looking forward to seeing the doctor! Please let the knee be ok! thanks for reading xoxo