easy bro. you are (95% sure about this) buying the wrong part of the pig. you absolutely need the shoulder. called different things..boston butt, butt roast, etc. dont let "butt" fool you. back in the day, it was called the butt of the leg or something.
you need the fat and connective tissue to break down and create the soft tender juicy roast. i bet you are either trying a tenderloin or rear hind part.
before you use a crock pot, brown the veggies. with pork you dont need to brown the meat. but it would help to brown the veggies before you dump everything in the crock pot. if you use any tomato paste, brown it at the end of your veggie saute.
This- Boston Butt in the crock pot, with onions and carrots= glorious!