Could it be that your LO is too active for the swaddle? I remember that Asher used to break free of his swaddle around the 3rd month.
Perhaps you could try putting him to bed without the swaddle? He might miss it for the first night, but if it starts to get better by the second night, then probably, you could say goodbye to the swaddle altogether. Alternatively, you could remove the swaddling cloth after he's sound asleep. Especially if he is already sleeping through the night (is he?), he is not likely to be fully roused when you remove the swaddle from him when he's in a deep sleep. I may be wrong, but it's worth a try, rather than risk something scary.
