Should I Have Went Under the Muscle? How Do I Get Better Cleavage?

I would recommend new lower profile implants silicone placed under the muscle. This should get you more cleavage. Your breast cleavage pre op appears to be 2-3 cm which is not bad.  

Based on your pre-op picture, I would have certainly recommended placing your implants under your chest muscle in order to give you better coverage over your implants.  This would have minimized the potential for ripples/wrinkles which could be seen or felt but also minimized the risk for developing capsular contractures, the constriction and distortion of the breasts which you seem to have developed.  You had a wide chest bone before surgery and this is what determines your cleavage.  Implants will give you volume but push-up/push-in type bras will give you cleavage.  Surgical attempts to give you cleavage may end with a bad result.  My suggestion for you would be to remove the capsules that have formed around your implants and re-position your implants into the submuscular (under the chest muscle) position.

but if you are developing a contracture, you should see your doctor about what options you have.  Cleavage in and of itself is not determined by whether your implant is above or below the muscle but more on how your pocket is created.  Your inferior medial pockets seem a little flattened and its speculation as to whether that is from capsular contracture or your pocket dissection.  Regardless, if you wish to fight the contractures, you will have to consider more surgery and you should know all of your options, including new implants, textured anatomic implants, and new pocket dissection.  Your nipples are always going to be pointing outwards as that is what you started with and your implants are only aggravating that.