Should I get another lift with implants? What are other options for cleavage and perkiness?

Unfortunately, you have not provided photographs. However, if you are already a DD then you certainly do not need implants but an adequate lift. The technique I recommend is The Bellesoma Method. This will reshape your breast tissue creating upper pole fullness without implants, elevate them higher on the chest wall and more medial to increase your cleavage. Vertical scars are avoided, nipple sensation (in 95%) and the ability to breast feed are maintained. Later, fat transfers can be performed if additional volume is desired.

Best Wishes,

Gary Horndeski, M.D.

Although you did not post photos, the problem, most likely, is your current implants are probably too heavy for your soft tissue and are beginning to sag. Do not go larger for this will just repeat at a quicker pace. I would suggest going down in size, and placing the implants behind the muscle for better support and upper breast fullness. Use a bra for cleavage.

You got it - the best way to improve cleavage is to pair implants with the lift. The lift will help tighten up the breasts but will not result in long term upper fullness. You need to add to the upper breast to improve cleavage, either implants or fat. You might not need to tighten up the pexy with the implants.
I would recommend you see a board certified plastic surgeon for a consultation. And you can certainly return to the surgeon who did the lift.
Best of luck to you!