Concern about lower back pain

Because I have a slender and long body shape, poor posture easily causes problems. Especially, I often feel a tingling sensation in my back, and sometimes my lower back feels like it's collapsing, making a cracking sound and hurting. I was so grateful when I went to an orthopedic surgeon after experiencing severe pain and was told it wasn't a herniated disc. They said that poor posture is the main cause of my lower back pain. So, I am advised to maintain good posture regularly and strengthen my lower back muscles.

I'm worried because I often find myself sitting awkwardly on the sofa quite unexpectedly.