Feel extremely groggy!

So basically the last 3 months I have been maintaining a pretty active workout routine. I usually went to the gym at least 4 times a week and would burn either 1k or close too it in calories. Consequently, I have lost 20 pounds. As of right now (last 3-5 days) I haven't been working out as hard, for I'm so busy with finals and I'm about to graduate college. I feel extremely tired and not just a "take a nap or go to bed early tired," but I feel really groggy. I also have been getting these dull headaches that will travel into my neck at times. I was wondering if maybe my body isn't used to not working out? I have heard of regular exercisers who will get depressed or agitated if they haven't done their exercise..kinda like a coffee addiction, and I wasn't sure if this maybe applied.

I guess the lack of endorphins is depressing? I know that dropping exercise massively quickly can increase stress and moodiness- but maybe it's more that you're focusing (lol JK stressing- doing my finals too) on the exams more and it's mixed in with added stress? Dont worry, you'll pick up after exams and your back exercising :) GOOD LUCK FOR EXAMS MAY THE FORCE BE WITH YOU :/