Iam 5 month pregnant.when i am standing for few minute i suffered backpain and also pain spread to stomach.what is the reason?

Strain: As your belly grows, your center of gravity changes and your back has to work harder to hold up the weight of your belly. Your uterus is suspended in your pelvis and all the ligaments that hold it in place have attachments throughout your pelvis, front, back and side. As your uterus grows, these ligaments are stretching and cause pain. Let's be honest, pregnancy can be painful! good luck!

Many possible: Most likely is simply the muscular and skeletal changes that happen in pregnancy. Less likely are issues with the pregnancy itself, but the only way to be sure is to check with your obgyn. Ultrasound can help check on your baby and placenta. Have him/her check a urine as well to make sure no uti. Good luck!