It may be that your body has started detoxing and so your blood-mercury levels are elevated more than before. This would be good in the sense that you're detoxing but bad in the sense that more mercury is being redistributed.

This weight gain can have several causes, among those are low thyroid. You could try something that supports the thyroid, and you should try drinking plenty of non-fluoridated water daily. As far as a definite specific cause of the bloating stomach; I really don't know, wish I did.

Thanks.