Labor?!?!?

Yesi • Artist Happily married, with one beautiful son
So I went to my 40 week appointment . My doctor said I was a tight 4cm dialated and she stripped my membrane. I had lots of pressure and when we got home my husband and I had sex and right around 1 I started having contraction. It's 4 now and I'm having them every 5 mins. It doesn't feel real. I wasn't sure if I was really in labor.  I feel like they're gonna stop any time now. I called the hospital and they told me to wait until I'm getting them every 3-5 mins.
Can any of talk share how your labor started.