I started noticing them at 22 weeks. They got stronger and more frequent as my pg progressed. They were definitely worse at work (on my feet, running around alot), to the point where my Ob asked me to sit down and rest at work if I noticed they were getting 'too' strong. Finishing work at 32 weeks helped, and I never got to find out just how bad they would become because DS arrived at 35 weeks.