Its is always hard and unwise to make a diagnosis and recommend treatment from one unclear photograph. You should see a qualified orthodontist in your area who has treated many cases with Invisalign for an evaluation. Assuming no complicating factors, your problem should be manageable with Invisalign.
Invisalign should be able to correct the orthodontic issues illustrated in the pictures. It is hard to provide a definitive answer with the limited information provided. There are many variables with Invisalign treatment. First and foremost is patient compliance with the Invisalign protocol. This involves 20-22 hours/day, 7 days/week aligner wear for the duration of treatment. Following the protocol to the letter increases your chances of achieving the result you are looking.. Second is your choice of doctors. In your case I would avoid orthoDENTISTS, general dentists providing orthodontic services. Find an Invisalign elite provider who is also an orthodontist. True orthodontists specialize in the alignment of the teeth and correcting non-ideal bites. They have advanced training in orthodontics from accredited orthodontic specialty programs above and beyond dental school. Orthodontists practice the specialty full time.
Invisalign does work and in the right hands, provides beautiful results for even difficult cases. I would suggest a second opinion with an Invisalign Elite provider who is also an orthodontist. Go on the Invisalign website to find a trained specialist who has treated hundreds if not thousands of Invisalign cases from simple to complex in your area.
I'm so sorry your teeth shifted. From the photos you included it seems as though your tooth front teeth have tipped toward each other. This is not something I would expect to correct using your retainer, even if worn full time. In the mean time please wear your retainers to at least keep the problem from worsening.Follow up with the doctor who originally straightened your teeth to discuss limited treatment to re-correct the alignment.. Once your teeth are straight again, please wear your retainers diligently as directed.