Baby formula and colic?

my baby has lactose intolerance when he was born he was fed for about 2 weeks it made him ill then i was advised to change him to formula so i put him on cow and gate still no luck then at 3 weeks of age he was diagnosed as having lactose intolerance so hes now on prescription milk. anyway hes now 31/2 months old and demanding lots of milk but the problem is its making him colicky and hes spitting up quite alot if he was on normal formula i would have given him a follow up milk because his formula is the thinist iv ever seen but unfortunalty there isnt one for the brand of milk hes on i dont think. i have heard alot about people adding a bit of baby rice to there babies feed. im just wondering if i should add some if so how often every feed or one or two feeds. if you think i shouldn't can you think off anything else i can do as i have tried colic remidies and they don't seem to work.