This is out of my comfort zone, but I'll try to help.
If we interpret your PTH test as normal, and calcium as normal, then the conclusion would be --normal parathyroid function. Even if we interpret your PTH as "low normal" there is no category that fits, since your calcium is normal. So the only conclusion I can see from the test data would be --normal parathyroid function.
I am curious about why the doctor ran the PTH test when calcium was well within the range. Have you had other calcium tests that were maybe at the very high end, or occasionally over the range? What, if any, symptoms do you have besides joint pain?
What did you mean when you said that your Lupus came positive, but all other Lupus tests came negative?
It doesn't appear that you have a parathyroid condition. While your PTH could be considered "low normal", your calcium level is not low.
What tests have you had for lupus? Lupus causes severe joint pain, as does hypothyroidism.
Have you had any thyroid function tests, such as Free T3, Free T4, TSH, thyroid antibodies, performed? If not, you should request these tests.