I will avoid lifting anything heavy.
Especially this early on in your pregnancy.
Just to be safe.
It could be from you lifting things wrong, or your muscles stretching. A good rule of thumb is don't lift anything heavier than you did before pregnancy. You can lift the same amount as you did before pregnancy because your body is used to it. But if it hurts, either lift less or make sure you're lifting with your knees!
I wouldnt life anything anymore. And it could b normal or sumthing. It depends on alot.. ask ur doc.