I just switched to the keto diet about few days ago because my husband's been on it for a while. I've been feeling just like what you have described almost every day, sometimes it curbs a bit, sometimes it's just awful.
I've been working out every other day moderately since I do not feel very well. Some people call it the Keto-flu, suppose to go away after your body says "what did you do?!".
A good way to feel better for me is to drink some bouillon/broth. I've found a brand "More than bouillon" Beef base that taste good almost like french onion soup. It's got almost no carb, so it's not going to ruin the diet.
One of our friends who's been doing this low-carb diet for over half a year said that he had never exercised during his time. Just make sure you drink enough water, watch your electrolytes. You can also take supplement pills instead of drinking the broth.
More info: reddit.com/r/keto/wiki/faq#wiki_adapting_to_a_low_carb_lifestyle
Hope this helps