Hello and hope you are doing well.
The common causes for difficulty in swallowing are enlarged tonsils and GERD. Gastro esophageal Reflux Disease (GERD) is caused due to reflux of acid from the stomach into the esophagus. It could also be due to disorders of the esophagus. You will need to consult your primary care physician who will examine your throat and may ask for some tests like barium swallow or endoscopy to determine the cause for difficulty in swallowing.
Hope this helped and do keep us posted.
No. An umbilical hernia would have no effect. A hiatal hernia may be what you're thinking of. You should see your doctor. It's hard to say if you need to see a gastroenterologist or an ENT.