Need a little help figuring out whats wrong. Options

[Frostii]

hello! i'm in need of some help, as i am kinda freaking out and worried about my little girl. i have a 9 year old, unaltered female jack russell who is as healthy as an ox. until recently when i noticed she became very lethargic and weak. she cant jump up on my bed anymore and that coming from a JR is alarming. she's been looking kinda mopey, she goes through these shivering phases, usually unresponsive to me and things outside, its hard for her to even shift when laying down sometimes, and she's been vomiting. her breathing goes from normal to heavy, not panting, but just breathing heavy. she is currently in heat, she is on her last weak, but still bleeding. she's drinking normally, and urinating regularly.

now i haven't seen how her poop is, as she hasn't gone to the bathroom today. most likely cause i don't think she's eating either. i will be taking her into the vet in a few days, but i would like to know if anyone can give me any ideas as to what could be wrong with her, and if there is anything i can do to help her until i take her to the vet.

thank you all for your help! i would love to hear from you!

~Frostii