HELP!!! I think my orchid's sick!

[Dillymint]

Hi everyone
I think my orchid is sick. I've had it about 7 years, in the same location for 4, and it's always been really healthy. Over the last couple of weeks I've noticed that the stems are going yellow and quite squishy, and there is an amber coloured liquid coming from the 'joints' on the stem (sorry, don't know the technical term!).
There is new stem growth and new roots. The leaves look OK, but aren't quite as fleshy as they were. I've checked for bugs and things and can't see anything odd at all.
Not sure what type of orchid I have, but it's white with a pink centre and is commonly available at garden centres for a few pounds.
This orchid is very special to me and I'd be heartbroken to loose it.
Any help or advice greatfully received - many thanks in advance.