Okay, the sensation you feel is known as Globus Hystericus and is a very common conversion symptom of people suffering from anxiety disorder. There is a lot of speculation in the medical community about the mechanism that acutally causes the sensation. Suffice it to say that we're just not sure and since it's entirely harmless, not much effort is put into identifying the underlying cause.
Many patients find that the sensation can cause them to become fearful of choking and it can very oftentimes lead to a panic threshold in some folks. It's extremely important here to realize that the throat is not actually becoming constricted at all, but rather only the sensation that it's occurring.
Relief is sometimes experienced by swallowing very small sips of water which can temporarily break the sensation. You just need to be aware that it's absolutely harmless and does not indicate that there is a growth or other occlusion taking place in your airway. Just remain calm and it will pass. You'll be fine.
Also remember my postings on heart palpitations regarding the specific entrance of a benign palpitation upon the normal sinus rhythm of the heart. Because of this factor, you can either sense a pause, a flutter or a thump. It's entirely normal and will never harm you.
Body position has a great deal to do with causing the Vagus nerve to become stimulated and send an inappropriate signal along to the heart, which results in a palpitation. Remember that the Vagus nerve innervates the GI tract as the gastric nerve and that trapped air or compression can cause stimulation of the nerve. Again, you'll be just fine. Always stay relaxed and know that the sensation can never do you any actual harm and can never turn into something more sinister.
Best regards and Good Health