Can an implant be put in backwards?

Technically it is possible to insert implants in the incorrect position but they have small marking dots that can easily be seen and felt but the surgeon.  It would be very uncommon to insert them in the wrong position.  The can flip after they are inserted but research studies suggest that this is also uncommon.

This would be a highly unlikely possibility but implants can be misplaced. Implants that have a particular shape can be problematic if they shift after placement.

but they aren't known to cause the symptoms you describe.  Best to discuss your concerns with your surgeon and find out if your surgeon has any suggestions for helping determine what is causing your symptoms.

Since most breast implants are more round shaped, their position is usually not detectable on the outside even if they have 'flipped'. Your description of symptoms sounds more typical of a tight pocket or some degree of capsular contracture. In most cases like yours, the culprit is the tissue pocket/capsule not the implant itself.

Implants can be placed upside down or they can flip after surgery though with a saline implant it would be usual to fill the implant and not know that it had flipped.Dr. Corbin

Yes, an implant can be placed upside down.   This may or may not be obvious.  Best to simply have a mammogram to study the implant.  My Best,  Dr C