Worried, so very worried

 Just got back from the emergency vet with Serendipity. She is the one between the keyboard and monitor in the icon picture. She is lethargic, drinking a lot, and some other things. It is pretty sudden honestly. Friday she was about her normal self and they yesterday nope. She is about 18 & 1/2 right now. I have had her since Sept 2001. They did blood tests and thyroid, kidney and glucose were good (the easier things to treat) her red blood cells and one type of white blood cells are low. The options are Feline Leuk or FiV but since she does not go out those are unlikely. They also said maybe an infection or inflammation. The other option is Cancer.  They gave us the option of intravenous hydration therapy, anti-nausea meds, keep her overnight and an ultrasound. We had subcutaneous fluid the anti-nausea meds and brought her home since money was a problem. We also did not think she would like being left over night. If needed tomorrow she can stay at our vet when we call to get an appointment. I am so worried. I am not ready for this. Just one more thing on top of everything else. I have a paper due tomorrow and I am unable to concentrate right now. I have college work I should be doing. My mind is so not on today. I was able to get a care credit card so that we do not have to worry about the cost which is one good thing.