You might just have sensitive gums. There are a couple of places where mine are really sensitive even though there's no disease or teeth issues around them. Because of the other tooth work (implants) I've had a lot of scans and probing of my whole mouth by multiple people so I'm certain there's no problems there - so it's very possible you have no underlying issue either.

Or you are one of many people that have been told how great their teeth are yet which have periodontitis/ gum inlfamation. (Source: My wife is an established dental hygienist keeping up with the newest approaches, going to advanced courses, visiting conferences.) If your gums are redish instead of light pink that's a good indication. If you are bleeding on regular use of interdental brushes/ flossing that's another hint something might be off.

The acidic, sugary drinks and food don't help at all. Drinking mineral water (no sugar, no extra acids) or to wash the mouth with regular water or a low concentration sodium bicarbonate / baking soda solution to balance pH after eating/ drinking something else would probably help. Of course, if not dissolved completely, the baking soda could act as an abrasive which wouldn't be that great for tooth health so probably just use regular water.

You don't need to invest much money to keep good oral health, it certainly is much cheaper to fix the problems that will arise if you don't, if they can be fixed at all. It however does cost effort/ time.

  > Nutrition is a key factor in this relationship. Frequent consumption of fermentable carbohydrates like gels, sports drinks, and bars increases the risk for caries, and acidic sports drinks promote dental erosion, especially when consumed during exercise and with low saliva flow.