You are recommended to visit your orthodontist so that he/she can do a detailed check for you.
One of the common reasons for a relapse is the lack of frequent retainer wear. It is of utmost importance to wear one's retainer after orthodontic treatment. I always tell my patients that "retainers are for life". If we want absolutely straight teeth, some sort of retainers may be required semi permanently.
If the shift is mild, a few sets of aligners can be used to fix it. However, if the shift is significant, then a retreatment may be required to realign the teeth to the desired position.
Depending on your condition, your orthodontist will recommend the most appropriate treatment option for you.
Best regards,
Dr Eugene Chan