He could also be meowing because he needs to poop. The neutering will help with the meowing as stated. For now just try to make sure he has lots of fluids.
He peed this morning but he still has yet to poop :/ unless he buried it really well. He did pass gas last night when i picked him up once but other than that I do not know how to get him to poop. I put some leaves and grass and pine needles in the litterbox.
I would suggest a quick phone call to the vet for a suggestion. They should be able to tell you something safe to help grease the system. Fluids are safe. You can do a search here on this site for constipation remedies. Let us know!