Take her to the vet. If she's intact, she could have pyometra which can be really serious.
Your description is way too vague for us to really have a good idea of what's wrong with her. Being "sick" is too generic a description. And you didn't say what's "all slimy"... so let the vet check her out, and if she's intact, have her spayed. Intact dogs are more likely to get some illnesses -!-