Keep your head up. If you didn't feel like you were adequately prepared, chances are that you weren't ready.
I took the Civil Structural, and passed (self studied). Here is what I did:
1. I spent about a month only going through the CERM. I went through every chapter and subtopic and tabbed it all so I knew what the hell was in there. I did problems here and there. I tabbed the index, table of contents, misc calcs that I saw repeatedly in sample problems. (1 month). This was the only thing I used in the morning session. (I used the AISC beam diagrams in the steel manual too for a couple problems)
2. I went through my codes and did the same thing. I tabbed every chapter and any subtopics that were important. I made sure I read through the codes to understand what is where. These codes include AISC Steel Manuel, ASCE 7-10, ACI 318-14, NDS, Masonry, IBC 2015 (I did not bring AASHTO with me). I got to know ASCE and ACI very well from reading it a bunch of times, I tabbed tables, equations, etc. For the afternoon session, I spent a lot of time in the ACI and ASCE codes just reading my tabs and figuring out where to go because the questions were look up type questions.
3. At this point, I had about 3 weeks to go. I did the NCEES practice exam like 4 times & did old ones too. I basically tried to cover at least 1 of every type of problem (i.e. horz curve, vert curve, beam design, etc.) but I didn't get to everything. I did the practice exam a bunch of times to get used to how long the exam is. I wanted to make sure time was not an issue - so I did the exam enough times to know my pace and understand what I need to do to have at least an hour to review. I ended up have plenty of time left over because I was pushing my pace during the exam.
4. One thing I suggest is Codemasters. They have these design laminated sheets that summarize processes for you. I had one for NDS wood design and that helped me soo much because I didn't have to flip through the NDS for all the factors. Codemasters has these sheets for NDS, Masonary, Wind Loading, etc. You can purchase all of them and they will be a big tool for you. You can put these in a binder. I think this is a HUGE help. Wish I had this for all the topics.
5. There is no way of knowing every problem. I saw some questions where I had absolutely no idea how to do it, and I knew it involved multiple steps. At that point, I just said screw it and moved on. I guessed. I really felt like if I spent 6 minutes and tried to solve it, I would've gotten it wrong anyway. So I guessed, and now I had 6 additional minutes to spend on a problem that I felt like I could get.
6. If you feel like you know a problem, do it and move on. When you are reviewing your work, confirm you answer with some sort of reference from your codes or CERM just to be safe. This helps you not miss questions you knew you had right.
I genuinely 3 months is good preparation. Spend 1.5 months tabbing your CERM and codes vigorously and really get to know your codes. then 1.5 months on practice exams and problems. Instead of counting hours, set goals to your studying (1 month you must go through entire CERM and tab, 1 week to tab and read through ACI, etc.) Since you are already in study mode, I would plan for April 2020. You got this.