I have a lower back pain again, this time from pulling weeks all morning. how to prevent it?

Posture: Change your technique. Obviously your back & you are engaging in a conversation.And you're not getting the message. See a physical therapist or your physician for advice--or, if that's the only activity that bothers you, get a gardener.

Pull fewer weeds: If pulling weeds causes you back pain, stop before it becomes severe. Other ideas-wear a back brace, take a Motrin before starting, strengthen your back muscles by lifting weights.