Do I need rest days?
Yes, but a rest day does not have to mean doing nothing. It means reducing training stress enough that your body can adapt, performance can rebound, and your joints, connective tissues, nervous system, and motivation are not constantly being asked for more.
Training works through stimulus-recovery-adaptation. The workout is the stimulus. The improvement happens when recovery is sufficient. If every day is demanding, fatigue eventually competes with adaptation, and the quality of later sessions falls.
A rest day can include walking, mobility, easy cardio, errands, or recreational movement. What makes it a rest day is that it supports the next productive session. If you feel worse week after week, rest is no longer optional background maintenance: It needs to be a more deliberately prioritized part of the program.