Hello,
The most important part of orthodontic treatment is retention phase, there are different type of retainer requirement as per different cases. If relapse has already occurred 2 times, surely there is a problem with the retention phase. You can go for the treatment third time, after getting your full mouth XRay done (OPG). If things are favourable, go for it & get a fixed retainer this time.
Next Steps
Go for a full mouth XRay (OPG)
Health Tips
Take care of the retention phase as per your orthodontist.