5 weeks post breast implants; are they too low? Are the nipples way too low? Are they likely to sag much further??

Your implants are settling in.  If you compare your before and after pics, you'll see that your breasts are the same just fuller, which is what the implants do: they add volume, they do not lift breast.  To address your nipple position, a lift would be required, or over time implants may descent more and sit lower, making your nipples look better positioned compared to the implants.Many women dream of not needing a bra, but the fact is, gravity is working against you 24hrs a day, 7 days a week.  You will always need a bra.I think you have a very nice result and need to be patient with your breasts while they settle in, and also understand that your natural breast position and shape is not changed with breast implants.  You had an augmentation of your existing breasts, not a breast reconstruction.

Your results look great so far based on your pre op photos provided.  You will see the implants settle into a lower position with time and the nipples will rotate upwards a bit.  The implants have weight to them and will only enlarger the breast in their existing position. Implants never "lift" the breasts.  In order to move the breasts into a higher position, you will at some point most likely consider a mastopexy.  Discuss your concerns with you board certified plastic surgeon at your next follow up appointment.  Best of luck to you.

Your implants are settling and you probably need a small lift to achieve what you are looking for. Good luck with your implants.