33 weeks pregnant cramping pain in the back of my thigh have the feeling i have to poop all the time?

Likely unrelated: 3rd trimester pregnancy can put pressure n the colon especially when the enlarging head is downward - that can cause feeling need to poop. The thigh pain is likely unrelated but may be a form of sciatica from lower back strain from the pregnancy. Your Dr or a good Physical therapist can recommend some gentle stretches for back & thigh Adequate fluids & fiber are important for bowels.