Sorry to hear you're feeling low. It's pretty common for low carb diets from what I've heard. It might be lowish blood sugar too. I experienced moodiness & irritability on IP. One theory is that your gut makes serotonin, a mood-regulating brain chemical, from dietary carbs. So cutting back a lot on carbs means less feel-good serotonin is made. There are supplements but I do not think there is evidence that they work for this problem.
Also there are hormonal changes that might affect your mood. Fat stores hormones that get released when the fat is burned for fuel.
A suggestion is make choices on the higher end of the allowed carbs. Make sure to have your restricted each day, and choose the higher carb allowed veggies. Eat unlimited ones if you like, but don't count them as part of your 4 cups. You should still lose fine if you stick to protocol. Just a suggestion
Good luck!