I feel your pain..... literally.... being 85% of the way through completely rearranging my bathroom in a similar fashion - and also as a DIY warrior rather than full time pro.
The good news is the last couple of days I have been able to get up from the sofa in the evening with slightly less groans and pains than I did after the first few days - I am either getting used to it or I am doing less work each day - I suspect the latter.
Are you having the clothing issue too ? - whereas I started off fully kitted out in various old clothes they have gradually been thrown out having got smelly and damp and I keep ending up doing work in more and more decent clothes as I am running out of old ones or I cant be arsed to change especially as I have to keep legging it out to pick up family etc. This evening I trashed my half decent Levis jeans and trainers !
The worse thing I find though is the constant stopping and easing off - sitting there just thinking, staring at the bloody thing, then over thinking things again instead of just getting stuck in...... the pauses are getting longer and more frequent .... must....keep.....going.....!
Keep going though as yours is looking a fine job and you can soon sit on the bog and admire all your hard work.