I agree with IJ. Honestly, man, I had myself convinced that bloating and 20 minute bathroom trips were normal if you were taking protein supplements. For me, it wasn't just cheap protein but added fiber like Inulin, Gum blends, other fillers and certain artificial sweeteners etc etc. I ate a breakstone cottage cheese from my friend's house this weekend and it was the digestive support style with added fiber etc and I was all bloated the next morning. For me, natural whole food fiber OK, added fiber supplements not OK.
If you aren't like this then God bless you man. It isn't fun. I use pure products like PF proteins or isopure and I'm OK. It just can't have anything in it but protein. So, for me it isn't the lactose (I'm fine with milk and dairy) it is all the extra stuff that I can't pronounce.