Squatting 250 at 138 lbs bodyweight would be something to be very proud of. I don't have access to my records, but I think my max was about 325 at around 175 lbs bodyweight maintaining very good form and going deep.

There's nothing to it really: squat heavy 2-3 times a week, increase the weight regularly in tiny increments, get plenty of rest, and eat lots of protein. If you're overtraining, drop back to 1-2 times a week.

Weight training is fun because results are directly correlated to how hard you work at it!