sure, if you swallow it.

whether it can cause those symptoms is a question ony your doctor can answer, given that no-one on the site is medically trained or familiar with your medical background.

please phone your GP at your earliest convenience and arrange an appointment to see them.

Yes, mucus from your nose SHOULD end up in your stomach.

The mucus linings of the nose and sinuses have a conveyor belt quality (as a result of ciliary activity) which causes the constant normal lubricating mucus to stream backward in the nose down into the throat where it meets another stream always being generated by the lungs. The combined flow from the nose and the lungs is designed to be swallowed, not expectorated, so the mucus can be decontaminated in the stomach and the components recycled by the digestive system.

Normally, this should cause no problems though. This mucus should be digestible by the stomach acids (unlike the mucus produced by the stomach lining which contains alkaline to resist the acid.

Source: http://www.otohns.net/default.asp?id=13085

However, if the sinus cavity is blocked with mucus, it becomes a target area for the growth of bacteria; this then becomes a bacterial infection. Again though, this mucus should then flow into the throat where it is swallowed into the stomach where the stomach acid destroys any hazardous bacteria.

See: http://www.wr-ent.com/6-noseCare.html

The symptoms you describe, bloatedness, discomfort and changes in bowel habits are commonly associated with Irritable Bowel Syndrome. You should visit your doctor as soon as possible to find the cause.

http://www.womenshealth.gov/faq/irritable-bowel-syndrome.cfm

The stomach is the natural disposal vessel for that and takes good care of the destruction!