Back labor/contractions

So, this is my 2nd baby and had back labor with my first. She came very fast after being stripped at my appmnt, less than 7hrs.....I thought it was cramps for the most part til I realized they were contractions. This time around I got stripped as well, 3cm at the Drs at 3 and and am now having back pain/contractions every 4-7mins lasting between 30s-1m. Obviously, I did not realize I was in actual labor with first til hours in... So I'm just wondering.. When do I start counting these pains as consistent and call to see if we should go in? TIA