I am lactose intolerant, what can I drink as a substitute for milk?

hey im 17, I always notice since i was like 4, that everytimeI drink milk I always have to go to the bathroom. I never there was a name for it, but now I know. But anyway, for sme reason I tried Lactaid "milk", and it made my go immediatly to the bathroom. why is that? and what can I drink now?