rat squeaking constantly

Question
my rat has started squeaking constantly, she has been doing this for a few days, she's also not been eating properly(for a few weeks)unless its food we give her outside the cage. We have tried new food as she has become bored of food before and changing it helped then, however this time shes still not eating. shes just over a year old, gets let out lots and gets lots of different foods. so she should be healthy. she is a lot less active now too and just comes out of the cage and sits beside me squeaking, perhaps she just wants to communicate or is bored and wants to find her food for herself!? she tends to squeak more when shes being petted. she isnt in any discomfort and generally just seems lazy but things have changed quite rapidly what with the squeaking...please help! many thanks

Answer
Rats do not normally squeak for no reason.   

Is this coming from her chest, perhaps?

You suggested that she is healthy since she gets a variety of different foods but it depends on the foods she is getting. High protein foods as well as foods high in fats are unwanted in a rats diet. What type of foods has she been on and which foods does she seem to want to eat for you now?
Do you leave food down for her at all times so she can self feed?

I am concerned about the noise she is making. I wish I could hear it.
Do me a favor and put her up to your ear, see if you hear the same sound as she inhales or exhales.  

Let me know so I can further evaluate her. Its hard to do this as you may understand, so I need you to be my eyes and ears in this case. :)

hang in there.....

Sandy