FWIW, with a tongue tie you can have a perfectly normal supply/letdown and LO may gain weight beautifully for the first few weeks. Foremilk tends to be higher in sugars (as I understand it) and hindmilk higher in fat content.
If there is a TT (anterior or posterior), biological nurturing or exaggerated latch may not make much difference as LO will often still slip down the nipple as the tongue is unable to move properly to extract milk from the breast.
If you are getting mastitis again, as others have already said, it is best to feed from the affected breast rather than pump so that milk is removed. It does sound to me like you have some issues with attachment/positioning which is causing these repeated episodes of mastitis, which is occurs when milk pools in the breast and effectively stagnates there (like a pond that doesn't move gets yucky) and infection sets in. However, if there is something like a TT at play, pumping may actually remove more milk than LO can right now, so you could give it a try.
In the meantime, ibuprofen is great for reducing pain/swelling (providing you don't have asthma/allergies to it, of course!) and heat before feeding and cold afterwards should help to get milk moving pre-feed and reduce pain/swelling afterwards.
Just as an afterthought, you said your nipples are sometimes lipstick shaped after feeding, are they ever a different colour too (purple, white, pink)?
