I asked a q and told fits endocarditis(murmur, fatigue&splinter haemorrhages).blood cultures&echo negative.cud it still be endo or maybe lupus instead?

See details: Did you have a tee (transesophageal echo) or just the regular 2d echo? I would not stop with the 2d echo. Murmur and true splinter hemorrhages suggest vasculitis or emboli. See a cardiologist if you have not done so already.

See below: There some organisms that are difficult to culture that cause endocarditis such as hacek organisms. I agree with the recommendation for a tee if you have not had one however; lupus can present with libman-sack endocardititis but that should be seen on an echo or transesophageal echo. You may need to see both a rheumatologist and cardiologist if you are not already.