Aww mama, I totally get why you're worried especially with your history! Light cramping at 5 weeks is actually pretty common, a lot of us experience it as the uterus stretches and everything adjusts, but since you had a loss before, it's definitely best to reach out to your OB just to put your mind at ease and get a proper check. The back pain might be separate (posture, hormones, stress kasi worried ka na) but your doctor can confirm lahat and give you peace of mind, kaya don't hesitate to call them even outside of your scheduled appointment, that's what they're there for!