Having Surgery Soon

Hi I am Samuel I am 19 this year

I will be having my tumor removal on my shin in 2 weeks would be a 2 hour surgery. And I will be on bed rest for 2 days. I won't be given a catheter but will be given a bed urinal but I have bladder shyness. As I am in a open ward (around 6 in a room).told them  I don't mind inserting it under cause of my shy bladder but they don't want. Told me to relax and i can be able to pee

Any tips for using a urinal in bed for bladder shy person?

The only thing I worried about is I can't urine and they need to insert it when I am awake 

Also I am always prone to constipation told them that also told me I will be giving enema most likely is I am constipated cause of my constipation history

Anyway to not get constipated 

Thanks 

not to get constipated*