Aww mama, I'm sorry you're going through this with the low lying placenta, that must've been scary. About the heaviness and back pain at 22 weeks, honestly that's something you really need to talk to your OB about kasi with your placenta situation, you want to make sure everything is okay and maybe get clearance on what movements are safe for you right now. A few of us moms get back pain early, pero combined with what you're dealing with, better safe than sorry talaga, your doctor needs to know exactly how you're feeling so they can monitor you properly. Hugs and take it easy, ha!