No worries man, sometimes it just doesn't work^^
I did a 2day waterfast before pfs and felt like DYING. Then another 3 day one and it felt pretty decent.
After pfs did 10 days and could easily go longer, but the 2nd time I did 6 days I think and I felt like going deaf, complete surreal worldview etc. and thought I gonna fall over any moment, so there had to stop^^
Guess the body tells u how long u can go here and there.