Dentist doesn't know what's wrong

[Jack100196]

I went to a dentist 2 weeks ago to do a regular check up because i felt a little pain and i noticed the upper left of my gums were swollen and around that area there was a hard lump on the gums where i had a tooth extraction a year ago. After the check up the female dentist told me that there was nothing wrong with my teeth and the lump was just the bone that was left after the extraction and the gums were swollen because of food touching the empty space of gums where i had the extraction. But she told me to come back the next day to make a crown for another tooth which was damaged.

I came in the next day, and this time i had a male doctor. I asked him to check my teeth and gums again and there was something wrong, i had to do 3 fillings on the right side which is not where my gums were swollen (and it's just weird that i still have cavity even though i brush and floss my teeth very carefully and use mouthwash, i don't drink alcohol, soda and i don't smoke). When i asked him about the swollen gums and the lump around that area, he told me the same thing the female dentist did, that it was a bone that was left after the extraction. He said come back 2 weeks later to finish the crown and he'd get the bone out.

The appointment is today so i went there. After finishing the crown. He took a look at the swollen gums area on the left side, and he took x-ray, but he said that he doesn't know why they're swollen and cause pain. I asked him what about the hard slump and he just said it was something different. He gave me Amoxicillin for a week and told me to come back if i still feel pain and the swollen gums don't go away.

Should i find another dentist? Isn't the dentist supposed to know what's wrong with my mouth and how to fix it? How come a dentist says there's nothing wrong during the regular check-up but when i ask another dentist to do the check-up in the same office, he says otherwise. I have health anxiety and now i'm just nervous that i may have oral cancer.