You are suffering from a impacted teeth. The gum swelling over it is pericoronitis, which subsides on medication but recur on accumulation of food debris beneath it or by getting sandwiched between the problematic teeth & it's counter part
Next Steps
Visit your dentist as soon as possible for remedy, because you are far beyond the age of eruption of the tooth, it's not coming out due to lack of space. It requires removal by a specialist
Health Tips
Prefer a Oral & Maxillofacial Surgeon for you treatment