It's stress related. I wake up around 7:30am every day because I need solid 2hours to "poo myself out", pee as much as I need and get to functional. I won't start or leave mine unless I know I'm done with my number 2 for the day
When I get longer bookings in the morning I make sure I don't eat anything too heavy on my stomach the evening before and have rather tea than coffee. It still happens to me from time to time that I have to poo once I'm ready and the client is 3 min away. If i see I'll be running a few min late I just text them say I got a "outfit malfunction" and just please give me a couple of minutes more. They don't mind if it's less than 5 minutes and it gives me enough time to wash and clean the toilet (I'm a bit pedantic about my toilet lol).
I always, always always have to pee last minute. I drink a huge quantity of water every day and I need to pee a lot. I know I'll have to pee last minute so basically I have my stockings and bra on, the rest is ready on my bed. Once I'm done peeing and washing myself (again), I need 1 more minute to jump into the rest of my outfit.
It's a routine question really and you'll get there. What took me 30 min when I started now takes me 10 minutes because it's become automatic (you just prepare and go through the motions without even thinking) and you'll get hold of it. Yesterday I had a guy in my street already and i still had to pee and finish my makeup, I pulled it off because I now know how to optimise every second when getting ready. All you need is practice and you'll stress much less