There are so many opinions on this subject. Some will tell you that you shouldn't weigh mid week as our weight fluctuates daily as well as hourly, others will tell you it's fine providing it doesn't send you into a panic if you see a gain or get excited if you see a huge loss.
Tbh I think it's down to the individual. I sometimes have a sneak peek but whatever the scales tell me it doesn't send me off plan if I see a gain or over ambitious and relaxed if I see a loss. However if I do see a gain then I switch things up a bit, get in some more sf foods, more water & less carbs before my true weigh in day.
It's personal preference but whatever you do, don't let it get you disheartened. X