It is not uncommon for one breast to heal, drop or settle at a different rate than the other as patients' breasts are rarely completely symmetric (especially in how their muscles are shaped, positioned or how they come off the rib cage as well as how their ribs are shaped- all things you cannot see until you get in there and all of which affect how the pockets need to be dissected for the best symmetry). It is possible for the implants to move up, down or out into the axilla after they have been placed properly, and it is possible that it may not drop because of capsular contracture (which most cases occur within the first 3 months after surgery) (in which case the firmness and asymmetry will start to look worse with time usually and not look better). 5 weeks is still early as it can take up to 6 months sometimes to settle (as it will vary greatly for different patients). I would recommend you follow up with your surgeon closely and let him know of your concerns. Best wishes.