How do I know if I have a hiatal hernia to you?

Requires testing. A hiatal hernia can be suggested by symptoms. The only way to know if you have a hiatal hernia is through testing - a barium swallow or upper endoscopy/egd are two ways to test for it.
Hiatal hernia. Upper GI x-ray and an EGD. The EGD is done by a gastroenterologist. Very common tests which can usually make the diagnosis of a hiatal hernia.