Well feedback doesn't get taken away, so I don't know why your old feedback is missing. However, I can address your current 15. Feedback only counts once from a seller within a short time period. I noticed you've had multiple purchases from the same sellers. Although they are leaving you individual comments, those only count once in your actual score.
If you are trying to increase your FB score, you should leave FB for your buyers. You've had 20 sales and 7 of your buyers left you FB but you haven't reciprocated by doing the same for any buyer. When you leave FB for a buyer, often times that will motivate them to do the same for you. By increasing your FB score, you will seem like a more seasoned seller. It will only benefit you as a seller and only takes a moment of your time. Also helps to weed out scammers as they think you are accustomed to the platform. Best of luck to you....
