Help!!! My cat is acting like he is in pain and there are no local vets.

My cat is 11 years old but still very healthy.  He is prone to injury due to he likes to protect his land.   He came in the house today and fell asleep like normal but when he woke he started howling loudly and will not let anyone touch him.  He seems to be holding his tail tight to his behind.  He also would not eat his favorite treat only licked it.  He is not howling the whole time and is actually napping now.  I live in rural area so we do not have a 24hr vet but I plan to take him in the morning.   I am just wondering if anyone else has seen this.  I am thinking he is severly constipated but have no way to tell since he goes outside to the bathroom.

I am posting from my phone, so I'm going to make this quick. While he could be in pain from many different things, my first concern is a urinary blockage. Males are especially prone. Please keep him indoors for now and take him in as soon as you can. If you notice him straining to urinate and howling more, this is an emergency.

As @GoHolistic said, it could be a blockage, tail injury, although constipation would be my last choice as this doesn't typically cause pain to the point of vocalizing, nd given that he is indoor/outdoor an injury seems much more likely.  Please update us after the vet visit.