Do I have a weak chin or bimaxillary protrusion?

Thank you for your pictures.  I think that you have lack of forward chin projection and possible some vertical excess to your chin.  You mid-face appears not to be an issue.

 The photograph demonstrates a weak chin profile.  Chin implants are manufactured in a variety of sizes and shapes which is best determined at the time of the consultation and examination. Chin implants are composed of Silastic, are inserted through a submental approach under a brief local  anesthetic. For many examples, diagrams, and more information, please see the link  below

You have midface and chin retrusion, not bimaxillary protrusion. Your teeth are in the correct horizontal position, it is your facial bones around it that are recessed. Midface and chin augmentation is the corrective approach for inmproved facial proportions.

If your occlusion (tooth mesh) is normal then it is usually prudent to camouflage a relatively week chin with augmentation. As an adult, your facial growth is complete and there are many ways that would be easier, less expensive and yield a satisfactory result than to undergo surgery that would reposition your upper and lower jaws. A lateral x-ray (cephalogram) is really the best way to diagnose bimaxillary protrusion. Judicious artful use of implants or even a horizontal advancement genioplasty may be the best way to give your face "foundation" by augmenting your chin. See a board certified plastic surgeon who is trained in craniomaxilofacial surgery to discuss your options. Best wishes.