Withdrawal after just 3 days?

I'm approaching my third day and today I've felt in a fog, extremely tired, and have head pressure/head pain, neck pain, leg pain, and some mild nausea. Could this be some initial withdrawal? While this morning I really wanted to check out some P, the craving has gone down throughout the day. My brain still wants to check it out, but I don't feel so excited by the thought of it at the moment. Earlier today I felt like I had to go to see what I have missed and to not forget what I had previously found a few days ago. I just finished some meditation and trying to stay strong. I have absolutely no urge to M right now.