Am I undoing my progress or am I imagining things

in this case listen to the measurements. Your brain can really play tricks on you at times and the mirror is most likely just you psyching yourself out. Dont stress about it.
Chris

I think you answered your own question in your question!

It is all in your head. If nothing has changed then learn to stop worrying so much about it. I mean you are in a size 1-2 and to me that's itty bitty, so be happy with your weight loss success and cherish every moment that you wake up the still looking the same. It is your choice to feel great about it

Don't let your mind play the games. You could really make yourself sick if you try to lose any more.

I have recently gotten to where I want to be... 5'9" and 129lbs

Going by BMI http://www.shapeup.org/bmi/bmi6.pdf
a healthy range is 130 - 165.
So you'll be fine if you gain a few pounds. Don't lose any more.

Any time I look in a mirror I think I have gotten bigger. My face looks bigger or my hips look bigger. I have not moved on the scale AND my clothes (and thus measurements) are fitting the same.

It's good that you're aware of your skewed perceptions. (stinkin' thinkin')
Keep paying attention to facts: what does your scale say, what is a healthy weight range based on BMI, your measurements, how do your clothes fit.

I feel so so much better but I constantly worry I will get "fat".

That could be a problem. Have you talked with your counselor about this body image difficulty?

Do you think this cutting back on exercise will lead to weight gain?

Doubtful.
As long as you're eating at maintenance (about 15 cal / lb*) you should be fine.

"Most weight loss occurs because of decreased caloric intake.
"However, evidence shows the only way to maintain weight loss is to be engaged in regular physical activity.
"To maintain your weight: work your way up to 150 minutes of moderate-intensity aerobic activity, 75 minutes of vigorous-intensity aerobic activity, or an equivalent mix of the two each week."

(The page explains moderate & vigorous.)
http://www.cdc.gov/healthyweight/physical_activity/index.html


* Harvard Medical School says 15 cal / lb is maintenance when you're active about 30 min per day.
http://www.health.harvard.edu/healthbeat/HB_web/calorie-counting-made-easy.htm

Whatever you did in the past worked great if you got to a size 1-2 and you are that tall. Luckily, you have age on your side right now. If I could die and come back to life again, I wish it could be back to my early 20's when my metabolism was still sky high, and I had endless energy.

You mentioned that you have changed up your fitness routine to now include strength training. That is most likely why you are appearing to be wider in some areas of your body. That could easily be new muscle definition, and that is a good thing, not bad. I say you should appreciate the new muscle you have gained, because that muscle is supporting your awesome figure and will give you much better posture than those ultra-skinny super models wearing size 0 who at age 35 will start packing on the fat and losing the bone density.

Again, be happy with where you're at and continue your great fitness lifestyle. If I knew then what I know now about fitness, then I might not have such a struggle losing these vanity pounds!

Measurements and photos will also help you stay on track. Watch those areas of where you hold most of your fat. For me, it's my abdomen. For someone else it could be their thighs or buns. If you see those areas growing in size, and you're not training them, then that's a good indicator that you may need to adjust your diet, right?

Someone else here mentioned it could be a body dismorphic issue. That could be true. I think anyone who's trying to get fit will have a bit of that going on. Remember that the way you see your body in a mirror is totally different than the way someone else will see you. You know every little flaw, beauty mark, stretch mark, etc. so naturally you're going to critique it. That's okay, but just don't obsess over it....don't spend too much time in front of that mirror! I know it's a girl thing to model yourself in front of a mirror while getting dressed, check out every angle of your body, etc., etc., but the more you do that the more stressed you will get over the most minor little flaws. You are not perfect. I am not perfect. Even that paid super model on the cover of Elle is not perfect! And remember, unless you're a professional model, you're never going to have someone sit there and stare at every inch of your body for a long period of time. So, they won't see everything you see nor may they care. Not everyone cares as much about body image.