I just went through two years of recurring colic with my gelding (had to euth him in May). Banamine saved him several times and let him relax enough to pass gas (had gas colic). I researched obsessively and got a lot of advice online.

Rub and massage around his left ear, it's an accupressure point that releases endorphins and will help relax his tummy. If he is down, reach over from his back to his stomach and massage his belly like you would for a sick baby (stay on the back side so he can't kick you if he thrashes or tries to get up). Once in a while give him a few light thumps like you were burping a baby, it helps things get moving. If he is standing up he might get some relief from a towel or blanket held on each side by two people, putting pressure on his gut from back to front and working in a light bouncing motion to massage from underneath him.

Stay with him and be calm and reassuring, you want him to be as relaxed and calm as possible to help him relax those abdominals and let things move through his gut. Pick up the poops in a baggie in case your vet wants to have them tested. It's not just for worms, he will look to see how dry it is and if his food is being digested properly. I hope he makes it through this, and you may want to consider a daily dose of probiotics to help him with digestion. He's older and has probably lost some digestive function due to his prior condition. The probiotics are good for a horse in his shape (mine was not looking much better when I got him) as they will help him absorb more nutrients and he will gain weight better for you.

Absolutely do not feed him until a vet has looked at him or you could make him even worse no matter which type of colic he has. Let him have all the water he wants.

I feel your pain, I went through this every 3-6 weeks for two years and it is emotionally exhausting. Sending positive thoughts your way.