Is he teething? Has he had bowel movements? If everything else looks okay and you are sure it's just separation anxiety...I would put him on another level of your house if you are able to and let him cry it out. It might take a while but just have the monitor on and don't go in. He needs to self sooth. If you keep trying to please him and make him stop crying he'll keep crying to get anything he wants. That's my advice...hope it helps!