Welcome to HCM,
See you are pregnant and some kind of blunt trauma
(Car Accident) and loose motions you should not ignore all these as due to loose motions you may get pain like spasm but we need to know about fetus and these tight contraction could be Braxton Hicks contraction( False labor pain
As you are having loose motions dehydration
can make them worse so hydrate yourself by adequately giving fluids in the form of ORS,and soups,buttermilk,and coconut water.
Even fruits and vegetables.
These loose stools
should be checked and if there is any cause it must be treated many drugs may not be safe in pregnancy
so consult your Gynecologist first.
If necessary a ultrasonography of abdomen and stool routine and microscopic examination will help.
For pain try deep breathing exercises.
Good Luck to you.