Hi Katriona, I have the exact same problem! I’m just under 3 weeks PO and also have pectus excavatum.
I had 275 overs and my boobs are actually touching in the middle (and getting a bit sore!) yours actually look much better than mine as mine are still quite high and the bottom of them is quite pinched in . I’m a bit scared they are never going to drop and always be an odd shape.
Sorry I don’t have any advice but interested to any advice you get. X