Is there anything I can do to bring my breasts closer together? More cleavage, etc. 3 weeks post op. (Photo)

These questions are best addressed by your operating surgeon. However, generally speaking under the muscle has initially less cleavage unless the operating surgeon takes measures to position the sub muscular implants closer to the midline--- as I would do. Without this manuever it will take massage to stretch the muscle in the middle so that you will improve your cleavage.

Cleavage width depends on your pectoral muscles and how wide apart they are.  Some women have a naturally wide cleavage.  If you look at your pre pictures, you had a wide-spaced medial border.  Going over the muscle with a wider base implant may be an option, or simply a push up bra can help

From the photos you posted, you had a wide gap pre-op so when you get a breast augmentation, you will still have the gap post-operatively with larger breasts.  It is your anatomy.  The implants should be placed behind your nipples so they are centered on your breast mound.  If they were placed more medially, that would cause your nipples to face outward. As your swelling goes down and your implants settle, you may be able to make more cleavage wearing a bra.  I recommend avoiding pec exercises if you have implants as they tend to move your breasts down and out over time.  No, your breasts do not appear to be tuberous.  ac

You have a gap preoperatively and you have gap postoperatively. Implants under the muscle cannot be placed nearer the midline than where the muscle insertions lie. Be careful with pec exercises and probably best to wear a support bra.

The gap is determined by your overall anatomy. When implants are placed under the muscle, the muscle insertion on the chest limits the implants medialization.