Why don't I get energy from working out?

1300-1600 cals a day while working out and breastfeeding?

Your question is also your answer. Strangely enough, the body will act fatigued when the energy input is dwarfed by the energy expended.

People don't get "energy" from working out... I mean... the whole goal of exercise is to expend energy and fatigue the body. When people say they get extra energy from working out they are describing the effects of chemicals released into the body during exercise. Endorphins cause a euphoric high similar to that brought on by a dose of morphine (though it is unclear whether the endorphin actually cause this feeling or just block pain and allow pleasure associated with neurotransmitters such as serotonin and dopamine to be more apparent. Interestingly, exercise is unique among "pleasure stimulators" because there is a certain amount of pain - at least 30 minutes or sustained exercise... maybe more - that must be endured to get the psychological benefits. Also, not everyone experiences them the same sustained "pleasure reaction"... especially if you exercise past the pain/pleasure threshold or never exercise to it. Of course having adequate fuel in your body is also important and it sounds like you aren't even close. The average woman requires 1800-2000kcal (give or take) to maintain weight, assuming a sedentary lifestyle. You are weight training and breastfeeding so ya... you probably need to give your caloric intake a second look.

I am not great at this, but let me see if I can help out. I see you logging cleaning and cooking for exercise, so it bring your extra cals up really high. From my understanding, the sedentary setting on MFP does include some daily activity, like cleaning, getting dress, etc. I would set it to the sedentary setting at about 1.5lbs lost at this point. Eat back 1/2 of your exercise cals. I just put in 1/2 of what it says. Maybe do at least 2/3 or 3/4 your breastfeeding cals. I am not 100% sure there. I do not log my nursing sessions, but I know with getting little sleep and nursing, I get hangry and worn down, more so that I like to admit. :laugh: I am not sure how to log the weight training stuff, as I have not gone to that point yet.
Looking over your dairy, food cals seem to be a bit all over the place too. I was doing the zigzag thing, and if you plan it well, it works. I do suggest never going below 1200ish net, maybe more since you are nursing. I change my zigzag routine because the eating less days where just not working for me, and now it is level cals and I eat back 1/2 exercise cals. So far it is working better for my energy levels. I do plan on having a cheat day once a week or once every two week. Also, the best advice, sleep when you can. It helps.
Good luck to you :flowerforyou:

I can tell when I work out vs. when I don't. I feel sluggish all day when I don't hit the gym.

That said, you are not eating enough to support breast feeding and working out. Even at your highest range of 1600....it's not any where near enough. Your baby could also be affected (nutritionally speaking) by your low calories. I would add another 1000 calories to your diet. Keep the calories clean for you and your baby's sake.