Lactose intolerant heeeellllp!!!!!!!!!!?

My son was fed for 3 days then I put him on cow and gate easy digest formula and he was a 'perfect' baby (unlike my first son who suffered awful colic) all of a sudden he stated with constipation and was in agony ping hard '' this lasted a week before the mw suggested a teaspoon of fresh orange in water which we did a few times and it helped a little but by 3 weeks he went the opposite way and started with diarrhoea! we hdnt given him the orange for 2 days when this started and firstly thought this was the course but after a week realised it wasnt, the dr said it could be colic and perscribed infacol which we had already tried and wasnt working, by 4 weeks he was in agony and having only what we can describe as 'adult diorreah' it was horrific and pojectile! My friend had some sma wysoy her daughter had been percribed so we went and got that by the next day his stools were looking a bit better and each day it has got easier to p and more 'normal' it has been 2weeks now and he has had 2 days of being fab, but, my hv and dr have said he should have sma lf instead due 2 the problems wysoy can cause which has worried me, will the wysoy have already damaged him and what if the lf milk backtracks him? I know i need to try it im just apprehensive!