Yes, it's common if you have symptoms of one type of digestive disorder, that you may/could suffer from another.
Many people with IBS also suffer with GERD, etc.
You nailed it when you said that what affects one digestive area could also have implications on another GI area. Whether this is connected to the central nervous systems involvement, I can't say..but what you're describing is more common than what you may think.
I'm one of the lucky ones that only suffers problems at one 'end' of the GI tract, so I can't help with suggestions about meds, etc, but wish you well in search of what treatment/regimen may be of help to you.