I have been having stomach issues, such as bloating , burping, weight loss, poor appetite, heartburn, and stomach pain?

Any upper gastrointestinal disturbance which is associated with poor appetite and weight loss at your age is a red flag. You need to see a doctor as soon as possible.

There a various causes of these symptoms but at your age, I find them concerning enough to recommend directly consulting a gastroenterologist for prompt and proper workup. Physical examination, appropriate lab work, endoscopy, ultrasound or CT scan may be advised.