Gimpy Toddler

So on Friday evening I noticed Brian was walking with a slight limp. He has been walking now for almost 3 months and the limp is a new development. At first I just chalked it up to him being so sleepy. I also didn't think much of it because he hadn't fallen recently and there was no swelling, no redness, and no bruising. Fast forward to Monday - he is still limping. Monday evening he was limping pretty badly. Badly enough for Jason to make a comment about it (which kind of freaked me out). So the doctor in me started moving all his joints and comparing legs and what not (stuff doctors do). Again, there was no bruising, no redness, no swelling. There was no difference between the two legs and all joints seemed to move freely and to the same degree on both sides. There was nothing in his feet, no cuts, no scrapes, no blisters. But he was still limping. Now toddlers don't just limp for no reason. As I started watching him closer it became apparent that he was favoring crawling over walking (something he hasn't done since he learned to walk), and he was asking to be carried a lot more often than usual. He was also fussier than normal and would whine while he was walking. Something was definitely wrong. I started doing some research online and came across something called a "toddler's fracture". Basically, its a low impact fracture that can happen if a toddler falls and twist their leg while falling. (Go here if you want more information on a "toddler's fracture".) Jason and I talked it over. I really wanted to take him to the doctor (mostly for peace of mind). Jason wanted to wait a few more days and said he didn't want me turn into an over-reactive mom. I agreed and told him I would wait. The next morning (Tuesday) I changed my mind and made an appointment at the doctor's office (after asking Jason). The doctor sent us to get x-rays and then we waited. I just heard back from the doctor and all the x-rays are negative. Good thing and bad thing. It's good because he most likely doesn't have a fracture, but it's a bad thing because we still don't know what is wrong with him. Right now we are treating him with ibuprofen. The doctor said that if he hasn't improved at all by tomorrow afternoon I have to take him back in. There is still a small chance of a toddler's fracture (sometime they take up to a week to show up on x-ray), but it's unlikely. I just wish I knew what was wrong so I could try and help him. I have lost a lot of sleep in the past few days worrying about him. I will let you know if anything changes.