SOS! I need immediate help. Please.

It is 3:48am right now. I heard some scratching noises out on in the kitchen so I walked out there to find my elder cat, 13 years old, squatting in a position as if he was trying to poop on the floor. He kept kicking his leg and he appeared to be squeezing hard. So I picked him up and took him to the litter box but he immediately left, walked into my room and promptly laid down. Now he is doing this thing where it looks like he is trying to push really hard, so hard that his whole bottom half scrunches up and he kicks his legs. He is quite uncomfortable right now. I will say I keep getting the smell of poop as if he is farting. I was pushing on his body and lower stomach to see if there was any hard spots but I can't feel anything. However after I stop pushing he starts doing the motion again a few times. Because it's 3:48am and the vets in my city are closed right now I can't do anything but sit here with him and worry. Does the smell mean he is severely constipated right now and is having a very hard time pushing it out, or is this something worse. 

I need some help fast. What can I do, if anything at all. 

I'm sorry if I didn't explain everything well I'm in a panic right now. If you need any more information ask me and I will tell you.

Maybe he is just constipated? Surely if he was in pain he would be making more noise. Has he eaten anything different? And if he's an outdoor cat he could've picked anything up. Keep an eye on him and if he's no better in the morning go see the vet if your worried

Ring the vets as soon as they open, and anal gland problems are a possibility.

Thanks for replying. He is an indoor cat and always has been. He hasn't eaten anything other than the stuff he usually eats. I'm thinking he is constipated but the movements he was doing were frightening to say the least. As of right this moment he seems much more comfortable. He had sprung up and left the room for a moment and then came back with a whole different demeanor. But I didn't see any presents in the litter box for me so I don't think he actually went. 

I will obviously be keeping an eye on him but another question I have for anyone on here. If it turns out by tomorrow it was just bad constipation what can I do to prevent it from happening again. He isn't a kitten anymore so I'm sure things that were fine for him before are no longer good for him. Are there certain foods or even a cat treat treat type of thing/supplement that helps aid easier bowel movements?

Aww bless him, let me know how he gets on, hope he's okay

Why not see what the vet says before worrying about consipation? 

How is your cat doing now?