thank you for your query.
first of all congrats on your pregnancy
the causes for pain in 7th month include-
1.The growing baby puts a lot of pressure on your diaphragm, liver
, stomach, and intestines. The additional weight can cause backaches
2.another common cause of pain is Round ligament.this is due to normal changes that take place as your body is transformed by pregnancy
To decrease back strain, make sure
1.to maintain good posture.
2. wear low-heeled shoes
3.use a firm mattress when lying down.
4.proper nutrition and exercise, to maintain your energy levels and increase your stamina for birth
5. Physical activities such as swimming fit well into late pregnancy.
hope these tips helped you,
wishing you good health