Large areolas, inverted nipples and stretch marks. What are my options? I'm 23.

It is possible to correct the size of the areolas with an areolar reduction. This is best done with a permanent internal stitch to mininmize the risk of it stretching out again.
The nipple inversion can also be corrected with surgery. This issue with this, however, is that during the surgery the milk ducts going into the nipple are often cut and this would eliminate the possibility of breast feeding in the future, so this would be better left until after you have kids.

From your photos it does not appear that you have any sagging but it is hard to tell as you might have your hands above your head in the second photo. You would benefit from an areolar reduction using a permanent pursestring suture to prevent stretching. There are 2 main techniques - the first where the outer cicumference is excised leaving a scar around the areola. The second techniques involves excising a disc of areola from around the nipple so that the scar is left just around the nipple. The inverted nipples could be corrected at the same time.

Your concerns can be addressed through correction of the inverted nipples and areolar reduction. Some, but not all of the stretch marks will be affected. The best place to begin is a consultation with a board certified plastic surgeon near you.