This problem, it belongs to the problem of digestion;

Considering that you have been in the gym for 3 days, it may be that XX is dry because of insufficient water intake, which increases the density of feces in the intestine and affects defecation;

If you get enough water, there may be something wrong with your diet. You may not get enough cellulose. This may be because you get a lot of protein and sugar during exercise, but you don't get plant cellulose.