Check the water quality for ammonia, nitrite, nitrate & pH and make sure that is good.
Do a big water change and gravel clean the substrate each day for a week to make sure the tank is clean. Clean the filter if it hasn't been done in the last 2 weeks.
Post a picture and if possible a short 20 second video of the fish swimming funny.
If it is too much dry food and ingesting air, then stop feeding for a day or two and see if it helps. If it doesn't help then it could be something else. Most internal problems can be hard to treat.