Yep, my DS2 was exactly the same. It was so tiring when they just want to be held all day. You haven't done anything to cause it, I promise! I parented all three of my babies the same way and DS2 was the only super-clingy one

Go and get yourself an Ergo baby carrier! It was my life saver for DS2 (and I wear it to bits now with DD). I have bad back and the Ergo puts baby's weight on your hips/waist so it doesn't hurt your back .