Not easy to answer without examining you.
It sounds like you have three options:
Remove your implants
Remove your implants and have a breast lift
Replace your implants with smaller ones, with or without a lift, depending upon the difference in implant size and the elasticity (tone) of your skin
Do nothing; stay as you are.
The change in volume from 350cc to 250cc may result in a half- to full cup size reduction.
A breast lift often reduces about 1/2-cup as well. Even though no significant volume is removed from the breast with a breast lift (mastopexy), the lift does tighten and narrow the width of the breast, which influences the fit of the bra.
In my practice, if a patient has saline implants, I will offer to incrementally deflate the implant with a needle and syringe, in the office, with a little bit of local anesthetic. This way we can see how much smaller an implant will produce the size the patient desires.
Unfortunately, this cannot be done with silicone implants.
You will probably be a bit smaller than you were before you had the implants, or at lest, you will be smaller than you remember you were.
Without examining you, it is impossible to assess the elasticity of your skin which will make an important difference in determining whether a lift is needed.
If you remove the implants and find you are unhappy with size or shape, you can go back for a second procedure to place an implant and/or breast lift). Though not desirable to have two procedures, you haven't "burned any bridges."