Is this the start of labor?? Advice anyone

Hi, this is my first post on here. I am 34 weeks and 3 days with my 3rd daughter, I had my second at 37 weeks but started dilating at 36 weeks. So anyways I have been getting Braxton Hicks in a daily basis and started getting contractions a couple weeks ago that the dr said was normal unless they lasted longer then 30 minutes. So last night around 2am I started getting contractions and didn’t think anything of it until I noticed that they were not going away after 30 minutes they lasted until 4:30 in the morning and they were getting stronger and lasting longer, I mean they were really starting to hurt. Now all day today I have been cramping and have a horrible backache that won’t go away and just don’t really feel all that good, and she feels super low. My drs office is taking a super long time to return my call and I just don’t know what I should do. Any advice would be nice. Also I am very very hydrated and have been laying on my left side all day.