Sheep still having problems a week after giving birth to two lambs?

One of our sheep is very old (approaching 10 years), and has just given birth to twins last Sunday. She is still walking around quite slowly, and is sitting down a lot. One of the lambs has died since it didn't have any milk but the other one we have been able to nurse back to health with hand feeding. The mother stays away from all the other sheep in the flock and doesn't respond much to hand feeding (she usually eats food out of our hands all the time). She is also convulsing like she is about to cough or have another lamb, and is has some thick bleeding coming out of her backside since this morning. Do you know what is wrong with her and what to give her to make her better? Thanks so much for any help, we're really worried!