The withdrawal symptoms is pretty common, though i don't know if there's a set time for how long it lasts. I would suggest from my own experiences that perhaps what happened to you is that you were experiencing what is called the void. It's the time we would've spent fantasizing, lusting, and looking at porn. Now it's "free" time, and we feel bored with nothing to do. No more pleasurable release surfing the web, etc. So, naturally we feel depressed and anxious. The solution is to find productive ways to occupy your time. Whether it's exercising, reading, or just plain shmuzzing, you need to find your own outlet. For now, and i know it's hard, try to move past this fall. I've found that some of my worst falls were those that came after long clean periods. I would ttheorize that it's the yetzer hara. He saw over the past incredible 29 days (!!!!!) that you are truly working hard at becoming a better cleaner person. So when he manages to get you to fall, he then goes into overtime to prevent you from getting back up. They say that what makez someone a tzaddik isn't that he never falls. Rather, that he may fall 7 times, but he got back up 8 times. It's time for you to show the yetzer hara what you're really made of. Brush yourself off, and just focus on moving forward. You can do it!