What do your workouts look like? Are you incorporating a weightlifting routine? Our stats are very similar, except I am about 6 pounds heavier than you and a higher BF% (@26%). What are your goals? I would think being under 25% BF and at the height and weight you are that you look good just where you're at.

I wonder if when you stopped working out due to the back injury and all the meds, if the weight you lost was some muscle. My husband was following MFP for a while, and unfortunately, was eating way less than he should have been following their recommendations. He did drop a lot of weight, and his clothes were all getting loose, but he also discovered he was a lot weaker in the gym with the weights. He has since gained back the weight and the strength, and now he fits fine in his pants. Perhaps that lightest weight you were at when you had to buy knew pants is not exactly the best weight for you. At one point (after the 4th child), I had gotten down to 133, which is the lowest I have ever been since getting pregnant with my first about 23 years ago. But then I started upping all my weights for workouts, and slowly gained 10 pounds to be around 143, although I realized that all my pants still fit me. That low 140's is where I am now. It seems my body, at the age of 48, just likes hanging in the low 140's. I occasionally drop under, but it just comes right back up. Low 140's seems to fit my lifestyle. All that to say, that perhaps fitting into those smaller pants would mean not being at a healthy weight. Working the lower body with weights does give you a "booty" and fills out those jeans! LOL!

As for calories. If you just started eating more this past January, and have yet to eat at maintenance, I would recommend trying to eat at maintenance for at least two weeks. Perhaps you could combine it with a heavy lifting schedule. Do you have Cathe's STS? Or any of her other heavy weights series? You may gain some during this time (I gained about 4 - 5 eating at maintenance or slightly above for 2 months), but when you then drop your calories and go back to 1700 - 1800, hopefully the fat will drop off and the muscle gained will remain. Watch the BF% number more than the scale's weight number.

I am no expert, but I hope I have made a little sense with my thoughts. Others may have better suggestions or explanations than me, but I hope it helps a bit.

Lifetime of yo-yo dieting.

So your body is more than adept at increasing, and lowering, metabolism.

Head on up to TDEE, however slow you want to go, like hang at Deficit level for 2 weeks and see there are no gains.
Then go half-way to TDEE, confirm no gains.
Then hit TDEE for couple weeks minimum.

If you lost none at the deficit amount, or the half way to TDEE, then 2 weeks at TDEE may not be enough.

You may drop to the deficit amount, and your metabolism may be more than willing to drop too. It's seen it before, it may be preparing for craziness ahead.

I'd say if no loss during the half-way to TDEE, stay at TDEE for 4-6 weeks while you lift heavy as main focus.

If you lose some at mid-level, stay at TDEE for 2 weeks.

And did the half-way level loss match what was expected for those 2 weeks. If yes, great, metabolism went all the way up, if no, etiher TDEE estimate is off, or metabolism is off.