Acting like in pain and red stuff on stomach possibly blood?

I have a mini schnauzer who is 5 years old. We never had her fixed and she went through heat about 2 months ago. This past week however I noticed it looked like her little privates area was swelling again. Then when she went out to use the bathroom I noticed she was wet all over her stomach with what looked like red mud but we don't have that in our yard or around our house so now I'm thinking it could be blood but I don't see where it would be coming from. She is also acting funny.
Not playful or barking like she usually does and when she tries to climb the stairs to go with us to bed she goes really slowly and acts like her hind legs or something in her back region is hurting. Please help its a holiday weekend and the vets are closed and I don't know what it could be. Is it possible she is just in heat again and bleeding a lot and hurting?
Also my husband thought maybe the blood was coming from her nipples but I don't know why that would be happening either.

NOTE FROM LINDA AND MAX:
All vets will have a 24-hour emergency number and surgery. Although it will not be cheap we recommend you get her professionally checked out.
It may be there is nothing seriously wrong, but better to be on the safe side - her change of behaviour and physical signs are a cause for coincern.
Good luck.