14 month toddler not sitting up or pulling herself up on her own?

My 14 month old daughter has always been a late developer. She only started rolling over at 8 months and I blamed myself for not putting her down for an independent play for the first 6 months. Now she's 14 months and although she's very wriggly, strong, can lift her head up, she only just recently started to army crawl and often stays on all fours in one place (she hasn't figured out how to crawl on all fours yet). She can stay in a sitting position if she wants to, but doesn't seem to like it and turns straight onto her stomach. I have also noticed that if she is in a seated position she tends to slouch. When I try to hold her up so that she can stand, again she's not interested and sometimes, but more than often not she doesn't even bother to put her feet flat. She's not interested in pulling herself up, she just a very happy baby rolling around and crawling around on her stomach. As well as being worried, this is becoming very tiresome and impractical, me having to hold her all-time like when we go to the public loo and she can't stand. I have just made an appt. with her paediatrician, but it is not until 29th June! I was also considering a chiropractor, anybody has an experience with that? Many Thanks!