Constipation 38 weeks pregnant

Vanessa • Married to the most wonderful & handsome man in the world! 👧🏻💞 born Oct. 23. 2016 & 👶🏽💚 born May 2. 2018 ♥️IG: DwyerBearFamily
I never really had a problem with constipation until recently! I have the urge to go #2 and when I sit on the toilet hardly anything comes out or I'm pushing and nothing wants to come out. 😫 Frustrating! Anyone else have this problem and why pregnant women have constipation?