Gum and even bone can grow back if the disease is well controlled and causes are removed.
You need to see dentist to have a scaling and deep cleaning in order to remove plaque; otherwise, hard to control at home since it's not a mild gingivitis (gum recessing), it may be periodontitis now.
Also, dentist can help you to find out WHY you have gingivitis or periodontal disease (smoking, diet, genetic, stress level, medication, saliva, "body's fighting system"...). You need to get rid of/control that risk factor to prevent the gum disease to progress.
good luck :)