Sluggish

If you're feeling draggy, and there's no other reason to be feeling fatigued, then eat more.

How fast are you trying to lose? With only 10 pounds to lose, I'd strongly suggest going with half a pound a week, and recommend that you eat back some of the exercise calories. (That's assuming you set your MFP profile's activity level based on your life excluding exercise, as MFP intends, or that you have an activity tracker sync-ed to MFP with negative adjustments enabled).

How many exercise calories to eat is individual. If you're highly confident in the exercise calories being reasonable, eat more of them. If you're suspicious that they're over-estimated, eat fewer. Pick a consistent percentage and stick with it. That will let you assess your results over multiple weeks, and make a sensible adjustment if needed . . . kind of like a fun science fair experiment, y'know? If we're inconsistent, we don't get good data, so adjustments are shooting in the dark.

I estimated my exercise calories carefully/conservatively, then all of them back during weight loss, and have done so for 7+ years in maintenance since. That worked fine, for me. (It was good practice for maintenance, too - I was refining my estimating skills along the way.)

Fast weight loss can have downsides, much as we all may want it to be fast so we can get it over with. (Note: Weight management is a forever endeavor, lifelong . . . not a quick project with an end date.)

For best healthy, strength, energy level, optimum nutrition, and more: Chose a weight loss rate suitable to the total amount of fat available to be lost. We can only metabolize stored fat at a limited rate before the body thinks we're in a famine, and adapts in undesirable ways. (This is not "starvation mode" where a person won't lose weight at too-low calories. I'm talking about the common-sense things like feeling fatigued so moving less, which is (1) a negative sign for health-risk management, and (2) eventually can make weight loss slower than anticipated at the given calorie level.)

I went with a slow loss rate myself, when trying to (re-)lose about that many pounds in maintenance (regained gradually over maybe 4 years).

Therefore, I know very viscerally that that loss can take a long time to show up on the scale, amongst routine daily water weight fluctuations that are part of how a healthy body stays healthy. You'll want to look at 4-6 weeks' average to figure out whether you're at the right calorie level, possibly longer. If you're an adult woman not yet in menopause, compare body weight at the same relative point in at least 2, perhaps ideally 3, different monthly cycles to figure out average loss.

Yes, it takes patience, but that slow loss can be almost painless, and it gives you an opportunity to find and practice some manageable changes in eating/activity habits that will keep you at your desired weight long term, ideally permanently.

Best wishes!

You're likely feeling slugging because you're not eating enough. You write you eat 1340 calories per day (do you eat them all or only a part of them). And you work out for 300 calories. That's pretty much the same as not workout out and only eating 1040 calories. And that's totally not enough. So I suggest you eat more. With so little to lose weightloss will be slow, but it doesn't mean it will have to be miserable.

What’s the worst that can happen if you try eating back your exercise calories? You’re unlikely to be eating over maintenance ick that you gain.

If you find you’ve got more energy and no longer feel sluggish then boom, you’ve got your answer, the overly restrictive calorie intake was the cause.

Many people find that actually eating a little more helps them to move more and so actually they not only feel better but maybe aren’t in much of a different place in terms of deficit. Eating more and moving more and burning more vs eating less but thus moving less and burning less.