Hey, thanks for the responses.
After you've pointed it out, I think you're right that it's not abdominal muscle hypertrophy. (I thought that squatting might be training me to push out my stomach.) Now that I think about it, I do notice my lower back is a lot more solid, so that might contribute to it. On top of that, some of it probably fat gain, as well as bloating.
buffalokilla - I weight train twice a week, hitting each body part one a week, and jog 4x week for 20 mins. My routine looks something like this:
Squats or Leg Press 3sets(14-10reps) 30 lbs or 90-115 lbs
SL DL 3x(14-10) 40-45 lbs
Donkey Kicks 3x(14-10) 15-20 lbs
Front DB raise 2x(14-12) 10 lbs
Lateral raise 2x(14-12) 15 lbs
Face pulls 2x(14-12) 20 lbs
Seated calf raise 3x(14-10) 45 lbs
Plank 2 sets hold for 1-1.5 mins
20 min jog
DB Press 3x(14-10) 30-35 lbs
Cable row 3x(14-10) 30-40 lbs(?)
Narrow grip pushups from the knee 3x(12)
Assisted chins 3x(14-10) counterwt 40-30 lbs OR Lat Pull downs 3x(14-10) 50 lbs(?)
Assisted dips 3x(14-10) counterwt 30 lbs
Hammer curls 2x(14-12) 20-25 lbs
Pullovers 2x(14-12) 30 lbs(?)
20 min jog
Plus 2 other days of running.
I know those weights are laughable but I am pretty small to begin with (110 lbs), but I'm focusing on form and on getting stronger.
OK, I'll give the squat rack a try - I'll go in at a time when the gym is less busy. I guess I find it a bit intimidating, but I'll get over it.