emmabu, to cut out caffeine, try drinking herbal and fruit teas, like redbush, camomile, elderflower, linden, raspberry, etc, there are loads of tasty ones on the market.
Dairy is indeed present in many foods, including non-obvious things like crab sticks, some sausages, ham etc. So, always read the label and check allery advice information on pack.
There are lots of products with soya used instead of dairy, but those who have intolerance to dairy protein can often have intolerance to soya as well as to other milks (goats, etc) too. So, try eliminating dairy altogether and then, if it helps, try dairy-free alternatives based on soya and see if it's fine.
BTW, it can take up to 4 weeks for dairy protein to clear off your baby's body, because it takes 1-2 weeks to clear off your body first and then another 1-2 weeks to clear off your baby's. And if damage caused to your baby's gut is severe enough, it also will take time to heal, so you might not get a big improvement immediately.
I'm currently not eating dairy, soya, gluten, fruit and sugar, so no cakes and still breastfeeding.
I eliminated dairy when my baby was 2-3 months old, then tried introducing it again a month or two ago (my baby is 7 months old now) and got a reaction again, so am back to dairy-free.
Try also speaking to your HV and/or GP. Mine were pretty useless , but maybe you are more lucky.