Clingy 16 month old

[Jodiesmum]

My dd2 is really clingy and has been like this for about 6 months. She can walk but prefers to be held all day and cries frantically when put down. If I leave the room she falls apart like a much younger baby would. She was premature and had a really hard time for ages so I wasn't surprised that she was clingier than DD1 - now though I'm starting to wonder how long it will go on! She's really heavy and the strain of carrying her so much is getting unbearable, plus I feel it's very unfair on DD1 who isn't getting as much attention as she needs. We went for a developmental check a couple of wks ago where I was told it was my fault she's like this because I've been over-anxious about her and have encouraged her clinginess. I really don't think that's true and it's not like I'm just going along with things now either - I do put her down and leave her to cry when I have to but nothing seems to be changing. I suppose my real worry is that there's something wrong with her though logically I don;t suppose there can be, otherwise it would have been picked up. Anyone else got experience of clinginess going on this long - and whether it could link to being ill as a baby?