Fussy Time

Life is good, but the past week was kind of tough. For some reason Jackson's nighttime fussiness came back. Every day this week starting at about 4:00pm he starts crying off and on for 2-3 hours. It's not just a whimper cry; it is a full blown scream. I feel like such a bad mom because I really have no idea what brings it on or what is wrong with him. I have no reason to think he is sick because all day long he is happy and smiling...then comes the evening and all smiles are gone. My suspicion is that he gets overtired and by evening he cant handle it??? But how do I make him take more naps during the day? Ive tried the "crying it out" method for nap time, but after 35 minutes of crying (2 days in a row) I couldn't handle it anymore. I also read "Healthy Sleep Habits, Happy Child" but nothing seems to be working. I'm probably making this sound worse than it is. Every baby has bad weeks, I know. Just wish I could figure out why my baby is crying in the evenings!