I feel like after my lip injection my upper lip looks longer and saggy. I look very old and I'm only 28.

 Hi, I have performed many lip augmentation procedures using dermal fillers or lip implants for over 30 years. Without non smiling photos of your lips before and after the injections with the dermal fuller it's difficult to comment on your lips.   Following my beauty principles, the lips should be full with the upper lip approximately 75 % the size of the lower lip for the lips to appear balanced. The lips can be augmented using a dermal filler or a Permalip implant.
Dermal fillers and lip implants offer a much more reliable volume for augmentation of the lips than permanent fillers or fat injections which are associated with increased, unwanted, side effects.
 Any "needle based" therapy which includes things like dermal filler or Botox can lead to minor, temporary changes in the shape of the lips due to swelling. This is typical mild in nature and lasts just a day or so.  Anything lasting beyond that should probably be seen by the Surgeon/Doctor that did the dermal filler injections to rule out lumps or clumps of filler.   While some minor swelling can occur after lip augmentation, there shouldn't be significant lumps and bumps in the lips.  Lumps and bumps after a day or two might represent excess amounts of the dermal filler in those locations.  You may want to ask the MD that did your lip augmentation to inject hyaluronidase which will dissolve the HA filler and even out the lips.  Lumps and bumps can be minimized, during lip augmentation, by using a uniform method of injection followed by massage of the lips (or injected area) to even out the dermal filler.
Hope this helps.