Feeling worse after going from higher healthy weight to lower healthy weight. Anyone else?

Early 30s 5’2 F here. I used to be slim despite being a couch potato all my life, and then the pounds crept on. So I decided to lose weight for vanity reasons.

Over the past 1.5 years I went from 125 lbs to 110 lbs. Started going to the gym for the first time 2-3x a week, focusing more on protein and getting my steps in. I reached my goal weight a few months ago and am very happy about it. Now my goal is to maintain my weight while still building muscle and staying active.

I enjoy my workouts and feel better about my body appearance-wise. But I also feel a lot more easily fatigued and low energy compared to before. I also get sick more often - I used to never get sick, maybe a small cold every few years. I went to get my bloodwork done but everything was perfect. I don’t feel actively bad or anything, but you hear about people going to the gym and having more energy and it has been the opposite for me. It’s frustrating because I’m still at a healthy weight, the same weight I had been in my early and mid twenties. My bf% isn’t that low and while I definitely want to gain more muscle and care less about total bodyweight now, I somehow doubt that that would make me feel better.

Has anyone else been in a similar position? Is there anything that helped you?