Just following up on many of the comments that ask, are you allowing enough rest/recovery? … I have a Garmin watch that gives a training status that I find a good indicator of whether my exercise is benefiting me or not. If my “load” is the same or going up and my “fitness” is going down it’s a good indicator that I’m not getting enough rest or that my current exercise has plateaued. I find it a good prompt to rethink what I’m doing.