I am sorry to hear you are so worried about Molly. I would definately take her to a vet. 10 is not overly old for a cat these days, and there are many things that could be wrong with her from just an infection to something more serious. Even if it is something serious, we can often sort the problems out if we can see the cat soon enough.
There really are a long list of problems that could cause these issues, and a vet examination may be able to determine some of them. Bloods and xrays may also be needed to make a diagnosis. Once you have a diagnosis, then you can know whether Molly is likely to recover or not.
Even if Molly is suffering from something terminal, it may be kinder to both yourself and her to put her to sleep rather than allow her to die - sometimes this is peaceful but sometimes it can be very painful and traumatic at the end, which would not be great for either of you.
If you have any further questions, please do ask me.
what can i do untill i see the vet?
There's not a lot you can do except keep her warm and comfortable and try maybe to get some water down her.