How to increase energy levels

29F and feeling really sluggish every day. I know I need to be more consistent with drinking more water (I tend to get pretty focused on my work or whatever task I'm working on and forget), and my sleep can be hit or miss. I'm trying to walk every day and get back into some light weight lifting, but I feel so tired all the time. I am not on any medication, I don't drink, and I also don't consume anything like energy drinks or anything that typically makes people crash. As a matter of fact, I don't drink caffeine at all. I try to stay away from sugary drinks like soda, I'm not a coffee person, and I've always heard tea dehydrates you, so I try not to drink it often (plus, I don't want it to stain my teeth). I mostly drink water. I try to eat mostly whole foods, though I do sometimes get lazy and cook something easy like a pasta or snack on something I probably shouldn't, like crackers. I try not to keep junk food around the house, though.

I just feel so energy depleted all the time, and I always feel like lying around, napping, and being lazy in my free time. My work is pretty inconsistent, sometimes physical and sometimes mostly office work.

TBH, I've had an energy problem since probably high school. I was on antidepressants back then and could barely stay awake during the day, but got off of them almost 10 years ago and noticed a positive difference right away. However, I still lack energy, just not as much as before.

Have you ever experienced this, and how do you combat it?