Doc won't stop labor if I'm at least 34 weeks

I'm just curious if any other ladies have been told this. I am 39 and this is my 4th pregnancy. All 3 prior were full term and healthy. I told my doctor I'm still working 5 days a week serving at a restaurant and sometimes it feels like someone kicked me in my pubic bone. It hurts to walk. I know it's from working because that's when it hurts the most. I asked if I should keep working and said I didn't want it to cause preterm labor. He said it was fine to keep working and it was because she is head down that I feel that pressure and that's also when he said he wouldn't stop my labor as long as I was 34 weeks or more. I thought they did stop labor if before 37-38 weeks! Kinda confused as to why he said that.