Do a kegel exercise, keep the tension throughout the whole exercise.(when you squeeze your vagina)
Pull down the lower back against the floor by rounding the lower back and squeeze your pelvic up toward the ceiling and keep the lower back flat against the floor without a gap.
Now pull your belly button in to your spine as far as you can go ,and lift your pelvis up toward the ceiling without lifting your upper back, only the lower back should be lifted.
Do as many lifts you can do and then rest and repeat
You can’t train this exercise too much, the more you can do it, the better results you will have