I presume that this was done Laparoscopically and in which case the gas and bloating is coming from air in the peritoneal cavity and not the bladder.
Very painful I understand and I really can't see how Buscopan will help as that drug relieves bowel muscle spasm which is not causing the pain in your case. You could try sitting up and massaging your stomach or maybe I might drop in and massage it for you;-)
I can't say how long it will last, but ai would be worried if it lasted longer than 3 weeks.