10k today was a failure

I figured that I have done a 10k a few times before so why not try it today. I did 5 miles last weekend so I figured I could do a 10k. I barely made it 5k. I had to walk the 5th-6th kilometer. I ran again at 6k to 8k, but then knee pain hit and I figured I should stop. I tried running again at 9k, but the knee pain was too bad by that point. I just could not. I am very disappointed.
I talked to my neighbor today about the soreness I continue to have in my thighs each day even though aside from my am workouts (which I have been too tired to do daily--I am lucky to get 3 in a week) I do 30 squats and lunges a day. My thighs this week particularly have just not recovered at all. They were still sore up until yesterday. I did about 10 squats yesterday and no lunges and none of either today. He said, and he would know, that this kind of soreness is usually nutrition related. He mentioned protein. I do not believe that there is an issue there, but maybe I will eat a few more servings of protein. I believe that the issue may be more iron related. With the heavy periods I have been having, I do not think that it is much of stretch to say that I might have iron deficient anemia. I actually have a lot of the symptoms which is funny because I thought those symptoms were due to estrogen dominance. They still could be. Without true hormone and hemoglobin tests who really knows. Apparently, though, a lot of women who have estrogen dominant problems have issues with anemia due to the "flooding" some experience. I experience the "flooding" each month and have for about 4 months now. It is getting better, but it is still VERY heavy. I also changed our diet from a lot of red meat to chicken due to my hubby's cholesterol problem. That is a recent change that could affect my iron levels. Here is to eating more spinach and beans. Thank goodness I like them!!!
Well, the secret reason why I wanted to test myself on the 10k is because I am seriously considering doing a half marathon in 9 weeks. With today's failed run, I have serious reservations now. I never challenge myself. I want to challenge myself. Every day at work is a challenge, but that is different... I want a real physical challenge. I was never an athlete. I will likely never be one, but I can run and like to run so why not challenge myself in that arena I figure. I do not know what to do....time will tell, I guess. I have another 2 weeks to decide...