I experienced the same pain as you do. I have done 14 LIF's so far and passed more than 4.000 stones. Between the flushes this pain was ALWAYS present to a stronger or lesser degree.
According to my own experience the pain is an indicator of stones that "want" to come out.
The thing that really calmed my pain was drinking a glass of a 50:50 mixture of olive oil and lemon juice first thing in the morning plus cat's claw tea using about 20 grams of the herb. It need to be boiled for about 15 minutes to be really efficacious. The effect was almost instantly.
And of course flushing, flushing and again flushing.
Good luck and blessings