How should I time contractions to know there are real contraction not bh contractions ?

Contractions are suppose to be painful and BH just uncomfortable

BH is just tightness they shouldn't be painful at all. If a contractions stops you in your tracks then you are having them.

It's more about intensity and progression. Surely you remember what the contractions felt like with your 9 yr old? BH is painless tightening and often stops with change in position or activity. True contractions will increase in pain and intensity over time.