6 week old kitten... rapid breath, unusually strong heartbeat, and constant need to rest

Hi, this kitten is about 6 weeks old and was abandoned by its mother (we live on a farm).

I took it and started feeding it 2 weeks ago. Since then we've taken in another kitten to take care of who is doing just great. No problems with the other one.

Back to my kitten-of-concern, Blue... she is definitely a runt. She was malnourished when I found her. I've been feeding her as often as she wants to eat. She gets winded almost too easily. She just lays down wherever she is and starts breathing very rapidly and very shallow. It's of concern to me because in comparison to the other one, she is very weak. I feel like maybe she was abandoned for a reason and I was curious as to what anyone had to say.

She also has been wanting to sleep in her litter and bites the cardboard when she goes potty... I was wondering if this was some sort of way for her to deal with her stress-- the sleeping in the litter and the chewing (even of her little house she has). 

Is there anything I can do for her here at home? Thank you so much; she's such a cute little thing and I've been trying to take care of her.

First, thank you for taking this little girl in! She is very lucky that you found her when you did!

Before you can even begin to address a possible behavioral problem you absolutely have to rule out a medical one. And, the only way to do this is with a visit to the vet. If funds are tight (I know you didn't plan to have two extra kitten mouths to feed) perhaps you can explain the situation to your vet and see if they will offer a discount. Many will when dealing with abandoned kittens. If not, try calling the local shelters and see if any of them offer low fee/no fee vet care. You could even ask them if they have any foster programs that you could be a part of. Many shelters will cover the cost of veterinary care if you house them. As an added bonus when they are old enough to be adopted out the shelter finds a home for them. They do keep the adoption fee but that is nothing compared to what you would save having to de-worm, vaccinate, and alter them out of pocket. 

Given the symptoms you listed there is little else I can think of other than medical issues so please, try and get her to a vet ASAP. You also want to get her seen because if she has something contagious there is a risk of her infecting the other kitten as well as any other pets that you may have. The sleeping in the litter and biting the cardboard could be ways of trying to reduce stress, but they are also just signs of being a kitten. If she checks out healthy at the vet come back here and we can all brainstorm ways to deal with that, but you can't put the cart before the horse. 

 Vibes that she checks out okay. Thank you again for saving her and the other little one! 

Yes, I too Im thinking it is a vet errand.  Possibly heart, but it is pure speculation.  Let the vet look and see, beginning with a cheap hearing and palpating.  If nothing apparently wrong here, he will go on with other tests, if it is perhaps contagious.

Now, being a inside kitty she doenst need to have same iron health as a semi-feral barn cat.  So say, a weak heart for example, doenst need to be a disaster.  The spaying will be more difficult, but not her live as such.

So lets hope for the best!

You did started in the Behavior forum and get moved here?

Good luck!

ps.  EB24, this here is your 999th post.  Next time you write anything it will be your Millenium post.