Wow sounds very similar to my evening.. I give DD a mix of rice cereal, apple and yoghurt for dinner at 5pm (that's all she'll eat), then bed at 7pm. She had a screaming session after her dinner, and TMI but turns out she'd done her first big solid poo. Maybe it was painful or just a strange sensation, but she wasn't happy. Anyway, I'm going to give her more breast feeds during the day to get her fluids up which will make her poos softer, and perhaps some pear for lunch too. She's just started to really eat more so we're still getting the food / breast milk balance right.

If you don't think it's poo related, maybe just try rubbing his tummy in a clockwise motion, bicycle his legs, or put him on his tummy to try and get the gas out. Poor little bub it's awful when they're upset and you don't know why... Good luck.