What could be causing a sporadic zapping pain in tooth then after a tight feeling in tooth and gum? this usually happens an hour after eating sweets

Zapping pain: This sort of pain needs to be diagnosed by a dentist. The common causes are decay, or a cracked tooth. Sometimes a neuritis can cause this. See a dentist for exam and treatment.

A Cavity...: ... that's one possibility. A cracked or loose filling, or a fractured tooth can also be the culprit. This will not heal on its own. See a dentist for definitive care.