Whats wrong with my 19mth old?

Well the last 2 nights i have tried to feed him dinner and he wont really eat anything, just kinda nibbles and then acts like he doesnt want it. all he wants is milk and hes happy. hes been waking up in the middle of night crying and then he just goes back to sleep on his own. He did feel like he had a little bit of a temperature lat night. The day before he had a 3hr nap and he was still sleepy afterwards and went to bed early. im going to call his doc here in a couple of hours when they open, but I wanted to hear from some of you moms if you have experienced this and what it could be. Please let me know. Thanks