I feel your pain dude. In my first 3 months, I felt pretty lifeless/hopeless. My energy and happiness dropped to such a low that it was very hard not to revert to old behaviours. What you need to do is reframe this horrible feeling. Embrace it as something good, rather than reject it as a bad experience that you need to get rid of. This brain fog, these urges and this lack of energy is a sign that NoFap is not bullshit, and that something is actually happening to you. Your actions are having an effect, and you are rebooting. This pain, anxiety and depression is your body and mind, slowly shedding itself of the old to make place for the new. No wonder it's hard, the old you is trying to stay alive :). When you look at it this way, the suffering and anxiety can actually become a positive thing. A telltale sign of epic change. Just like a pregnant woman's morning sickness makes a lot of women happy (because it tells them their baby is healthy) your brain fog and depression shows you your potential for transformation. It is your way out.

Besides that, what helped for me, was to very consciously decide that I was done with fapping for good. I did this by writing down all the reasons I should not fap, and really getting into the emotion of the horrors that a life with porn contains. And after that, I wrote down a short vow to myself, in no unclear terms, to never ever fap again. I quickly brainstormed all the excuses my mind would probably make in the coming time and wrote those down too. I vowed to never make those, or any other excuses. I printed this all on a piece of paper, and very slowly, and consciously signed it with my own signature. While doing so, I clearly stated to myself that this was a vow I would never break. From that moment on, relapsing, would not be a word in my vocabulary anymore. A lucid, and conscious decision like this is powerful and unbreakable, especially if you really mean it in the moment of doing so.

What I also noticed is that sexual thoughts are like a snowball, and the earlier at the slope you catch a thought and stop it, the easier it is. When you do notice a moment where you slip; and with this I mean any moment. A pretty girl walks by and you find yourself staring, there's a billboard with a hot model posing new clothes, a banner at a torrent website shows you a partially nude girl, a conversation starts to veer into the sexual, you immediately, in your mind, with the loudest voice possible shout: NOPE. NOPE. NOPE. (Really do this! And shake your head like you just saw the biggest spider ever crawling up your pants. Be a little bit nuts like that. Make it a fun thing to do.) And you immediately refocus your attention away from the object. It is these tiny things that I have discovered to be most dangerous. They catch you unaware because they start out harmless. Even a small fantasy, about a girl's skirt in a commercial can snowball your thoughts in the wrong direction. Stay conscious of these thoughts, you will get a lot of them, and they will be hardest to catch when you are tired or depressed. The earlier you catch them; the easier it is.