Mitzy, any formula can cause constipation, but the golds are more likely to do so. Generally the first thing to try with constipation (apart from changing formulas, which you have done), is to try and get the baby to drink more, and especially more breastmilk, as this has a laxative effect and will the best way to end the constipation.

Do you mind me asking if you have been seeing a LC at all? Big babies shouldn't need more milk than their mums makes, the whole way bfing works is supply and demand - the more the baby drinks, the more milk you make. So you should, except in some unusual circumstances, always have enough for your baby, no matter how much they are drinking. Unfortunately complementing with formula can be the cause of low supply, or worsen it, as the baby is drinking less bm, and you therefore make less. This is something that can be overcome, especially with the help of a good LC, if you are interested in bfing fully. The first step is to increase the number of bfs. The sooner you start to do this, the easier it will be to build your supply up again. If this is a path you are interested in (and of course it is totally up to you, I'm just putting the information out there in case you didn't know about your options), the ABA helpline on 1800 mum 2 mum (1800 686 2 686) can give you more information also.

All the best with it all. I hope the constipation settles quickly.