Hey amalyse, somebody recently had a very similar post in the 'Coping with Infertility' thread, here is the
link Hope it works!
As others have said, you are being a great friend for wanting to know/understand better what your friends are going through and how to support them.
I'd say be honest with them, tell them that you are thinking of them and sometimes when you are having a hard day you don't feel like you have the right to 'complain' to them because you realise that your hard day is nothing compared to what they are going through...at least that way your friends will know that that you are being very considerate, and so they might encourage you to be more open and feel free to rant about your own 'issues'. When we're going through IVF we do feel that some people do not realise how fortunate they are, but it doesn't mean we don't appreciate that others are finding it hard to dela with a screaming teething bubs or just feeling exhausted from looking after a little one all day... it's just putting things into perspective and knowing that we all look after our friends no matter what situation they are in.
There are some good links in the thread above, hope you find them useful =)