Is it to late to change OBGYN?

I'm 18 weeks today and my OBGYN and his office is making me furious and feel like I'm on my own. I went to see him for the first time when I was 12 weeks and he just didn't seem interested in his work. He came in did his doppler and left. The nurses keep giving me run arounds when it comes to scheduling appointments and I don't know what to do. I still haven't even been scheduled for my ultrasound at 20 weeks and I've called the office 3 times about it and all the nurses and workers keep passing the phone around. I just don't feel like I'm in good hands and I'm worried.