Im pretty sure everything is the same except for the fat content and calories, which apparently is what is so important about it to a baby. Everything ive read says all other nutrients are the same. so i assume the lactose would be too. If he is lactose you could always try goats milk. I know some ppl who have used that for their kids but i thought it was just for GERD babies-not sure about lactose. I know my mom said when my sister was lactose (it was only as a baby, eventually she was fine), that she was put on soy formula. But i also know soy is a last resort sort of thing. When she would BF she (my mom) had to cut out diary completely. Are you gonna take him to the doc? Has he tried any other new foods? When you nursed him, did he seem to have a problem when you drink milk? Usually, if a baby is LI they will show a reaction when you eat/drink something with diary and then BF.
I found this. I havn't read through it but looks like it would be a good read:
https://www.babycenter.com/0_lactose-intolerance_1201464.bc