Back ache , feel like cramps. Normal?

I am 20 weeks 4 days pregnant. I had level 2 scan 3 days back , everything is fine. I had urine routine test also. The report is also fine. Ph is 6.5. My concern is that after every 4-5 days i have back cramps which i feel like coming to sides and in front also sometimes. And sometimes i have left rib pain while lying on left side. This is happening from last 4 weeks. Earlier my gynac suggested to have Pan-D but it did not work. The pain comes every 4-5 days. It is like cramp which comes and go for a day then 4-5 days will be normal. Somewhat like period cramp. Unable to explain. Unable to find the pattern. I dont know what stretch pain is but it did not feel like stretch pain. I only eat home cooked non spicy food.. Are these pain / cramps normal?