At 17 weeks you should have good diet and plenty of oral fluids .constipation to some extend is expected in pregnancy as the digestion is slower and assimilation is more.but if you are still uncomfortable then you can try a laxative syrup at bed times to make stool soft and not to strain.increase fruits like musk melon / water melon in the diet as it contains lots of fibers

Take duphalac syrup_3 tsf at bed time

Syp Duphalac 4 spoons at bedtime with a glass of water Take 3 oranges daily Take 3 bananas with milk daily Change the iron preparation if it is the cause of constipation

Don't strain too much while pregnancy! Constipation is common complaint If u strain much than u can chnaces of bleeding n having piles! Have plenty of fluids throughout the day Fibre rich diet Avoid junk food