first off, way to go mama with breastfeeding your twins!
you've gotten lots of good advice. I've had similar experiences with my daughter. I wondered about diet changes and such but so far things have greatly improved with some adjustments to our nursing routine. I do the cross-cradle hold with her and lean back with her on a boppy so that she has to nurse downhill somewhat - gravity helps control the flow. pulling off and catching the initial letdown into a burp rag works well too. what are his poopy diapers like? my doc said that she's never seen a case of milk protein allergy where there wasn't an indication in the diapers - very mucousy and green and sometimes slightly bloody.
you might google hyperlactation syndrome and see if it fits your experience - if baby's getting more foremilk than hindmilk, it can actually cause excess gas and stomach cramping. this seemed to be the case with us - you might try feeding him on the same breast for 2 feedings in a row (i know this might be tricky with twins but maybe not?)...that way he gets more hindmilk the second feeding on the same side.
we also swaddle our girl, and try to do lots of belly massage (gently massage around the bellybutton in a clockwise motion) as well as bicycling legs to help get the gas out.
best of luck to you!