If a baby is latching correctly, it has it's mouth wide open, and it will latch onto your aureola, not your nipple. When bub is attached, then the force of the suction pulls the nipple out, into the babys throat. So the shape and size of your nipples is actually petty irrelevant.
When my sons were tiny, and would slip off my breast, I would make sure I dried my breast every time I tried to latch, as your breast very quicky gets covered in slippery milk, and bub just slides around. Drying the breast gives them a fighting chance to latch.
I would also press it slightly flat, like a biscuit, so it was an easier shape to latch onto for their mouth.
All the best, I am sure you will breastfeed marvellously. smile
homebirthing mum to three boys!