5'1, 100 lbs. Over the muscle 250cc high profile implant to under the muscle; what are my options?

I've had my implants since Dec 2014 and not happy with the results. They're very firm and a bit large for my frame. My doctor advised me to reduce the implants to 150cc HP for softer, more natural breasts. But I'm thinking of having unders but he doesn't recommend it since I have saggy breasts and I might develop double bubble if the implants will be put under the muscle. Or will it be better if I'll go for 200cc moderate plus to have more natural breasts. Pls doctors, im desperate for advices