New symptoms during doxy

Hi all I'm 6 weeks into doxy after find img a rash, the last 3 weeks I've had shoulder pains on the right on and off, as this is a new symptom does it mean the abx are not doing their job?

Or is it a herx? The pain comes in short waves then disappear, kind of like contractions during labour ( no where near as intense painwise)

It is really hard to tell at this point - just keep treating...if it continues and you get more symptoms...you may be dealing with a co-infection.