My dd is nearly 11 weeks old and her head at he back is quite flat. I’ve mebtioned it to the health visitor and she said to try and put her in different positions but over all she wasn’t to concerned. My only problem is she will do tummy time a few times a day when she’s playing on her mat but she hates it and I’m conscious she cant spend loads of time on her front. She’ll sit in her bouncer for a bit as well but with her still being little she has to spend the majority of time on her back. Has anyone else had this and did it resolve itself as they got bigger and started to sit up more?