Can pushing Breast together to retrain the muscle help at this point or is it too late? would you recommend a wider implant?

From your description, your implants are submuscular. Since cleavage is determined by where the pectoralis major inserts on the sternum, pushing on your implants will have not effect on their ultimate position.  As the muscle lengthens over the next several weeks to accommodate your implant, the implants will become a little more mobile and in a bra you may be able to get more cleavage by pushing them together.Placing a wider implant in the same plane will cause your breasts to extend around the side of your chest, but won't change the cleavage.  The implants could be placed subglandularly, but that has its own set of possible complications.  Be patient (3-4 months) and let everything heal before making any decisions.

It depends on your body ... the width between your breasts is partially dependent on the size (width) of your sternum as implants can not be placed any closer than the width of your sternum. It depends this and the width of your breasts as to whether a wider implant would be helpful. You may consider a second opinion to ensure further surgery will give you your desired results. Put manually pushing your breasts together or wearing a strap will not help.
Good luck, Dr. Luong

Pushing your breasts together will not do anything. If the implant is under the muscle, the insertion of the pectoralis muscle near the center of your chest is what is preventing the implants from moving any further toward the center. The muscle will have divided more and this may or may not be a good idea depending on your anatomy. Simply placing a wider implant will not solve the problem.