I agree with IADad, first check for any possible complications. One thing to consider would be ear infection - its almost impossible to tell without a doctor checking. Some kids also teeth this early, if you think that is a possibility you could try some teething tablets or rub his gums a little with your finger, putting a little pressure on them, maybe some infant Tylenol just to rule it out. For some reason when you get tired anything bothering you just intensifies that much more, so you might not notice the problem as much during the day. Also, any changes in his diet? That could contribute as well. Or if he is having a growth spurt, he might be hungrier? Have you tried giving him a little extra in his feeding before bed? Either way growing pains are uncomfortable.
Did you make sure he's not hot or cold? What happens if you walk around with him, bounce him, rock him? You could try swaddling him, some babies are soothed really well by that? If he might have a belly ache, you could hold him with your arm around his belly and him facing outward from you, and kind of walk around with him like that and kinda bouncing him? lol I had an insanely colicky baby, so I remember having tried it ALL. You could also try turning on some quiet music so he has something to listen to to distract him? What does he think of the swing?
There's lots of stuff to try, but sometimes babies are just cranky. Its so hard to tell what is bothering them! If only we could read their minds haha. If nothing else I remember getting a really good suggestion from someone (I think on this forum, a long time ago) about not getting frustrated. Its SO hard not to want to rip your hair out when your baby wont stop screaming those ear piercing screams and nothing you do helps. Someone said to pick up a couple pairs of ear plugs, and I have to agree. Just so while you're carrying him around and trying to console him and he's screaming in your face you've got those ear plugs in to muffle it. It doesn't cut the noise out completely, you can still hear everything, but its a lot less painful lol. It can take the edge off of the frustrating screaming. I wish I had tried it with DS.
Good luck, and don't worry its only a phase and you'll be past it before you know it (of course there will always be something else lol).