miscalculate my pregnancy... thought it was preterm labour

At just 8 months into my pregnancy... I suddenly felt intense cramps. Contractions all night long. I was terrified of going into premature labor. Coincidentally, I had been doing some heavy activity that day... and was a bit tired. I immediately went to the hospital with my husband. And you know what? Turns out I was really about to give birth. And want to know more? Turns out my pregnancy was actually 9 months! I was a month ahead of my estimate not because of premature birth, but because of MISCALCULATION......... oh my, I felt so relieved because I had actually planned to go on vacation before giving birth. But luckily, I was still at home and had easy access to the hospital. Be careful and always make sure your pregnancy is safe, parents. Anyone had a similar experience?