First of all, I'm very sorry that you are sick, that you have just been diagnosed with lupus, and that you are concerned about your diagnosis and that the doctor is unavailable right now. I'll try to explain this in a way so you can understand, however keep in mind that you may be feeling upset right now and when we are upset, it is sometimes hard for us to make sense out of things because our mind is just whirring too fast. So you may want to take a break to do something relaxing and then come back to this later.
As it happens, scleroderma is only diagnosed based upon symptoms and not by lab tests, because lab tests can be misleading and they can be false-positive and even false-negative. So actually that lab report is a bit incorrect in that a person does not automatically have scleroderma if they have a positive SCL-70 but no specific scleroderma symptoms. It is my understanding that if a person has a High (positive) test they might be prone to developing scleroderma, but a bona fide diagnosis of scleroderma requires certain symptoms.
Also, it is common for even entirely healthy people to have low levels of all sorts of antibodies so levels that are not "high" or "positive" are Negative. Period. So if you have a "3" on the SCL-70 but positive is anything greater than 29, it means that you are negative for the SCL-70. You aren't "a little bit positive", you are negative -- on this particular test, at this particular time, at that particular lab, given their particular measures and standards.
Please note, that is not the same as saying you don't have scleroderma because if you did have symptoms exclusive to or very indicative of scleroderma, then you would (or should) be diagnosed regardless of what any of your labs are.
Now, please keep in mind here that I may be wrong -- I often am! -- and that I have not even sent in my five bucks for my Internet Medical Degree (IMD) yet-- but to my rather lame reasoning, if you are trying to cut the deck of cards in favor of a scleroderma diagnosis, based only on malabsorption, there is a logic gap, because weight loss can be caused by a zillion conditions, including POTS, which you already have, and weight changes are also to be expected following pregnancy (due to hormonal changes) and especially along with stress, which you have had more than your fair share of in the past year. If you take all three together, POTS plus hormonal changes plus massive stress, you almost have a recipe for guaranteed weight changes, and there is hardly even any wriggle room to add yet another reason for weight changes to the diagnostic mix.
Then, of all the possible reasons in the whole world for weight loss, scleroderma would have to be near the very bottom of an extremely long list, because scleroderma is so much more rare than hardly anything else. You would probably have better odds of being struck by lightening on a clear day while standing on the corner of Hollywood and Vine from 11:05 to 11:06 on a Tuesday morning. Worst of all, the mere thinking that it could possibly be an often fatal disease that is causing your weight loss, would be more than enough for most of us to lose our appetite.
And, all this might be causing you to lose sight of the fact that you should be dealing with real-world issues such as working with your doctor to establish the best possible health practices to keep your POTS, and your new diagnosis of Lupus, under control.
No matter what is causing your weight loss (even if it is, on the very off chance, due to scleroderma), the only remedy for it is probably going to be to increase your food intake to compensate for it, and to reduce your stress levels because stress can worsen any g.i. issue.
If you get down to dangerously below normal weight, then they will either send you for treatment for anorexia and/or they will begin tubal feeding. One of our members here has scleroderma and has been on tubal feeding for years, and yet she still runs a very lively home complete with geese, and even produces a radio program about cooking and recipes. I have another friend who is a grandmother with scleroderma, and she works full time and has been on tubal feeding for probably about ten years now.
So what could be the worst possible thing that could happen to you? You could have scleroderma and be on tubal feeding and then perhaps have mandatory geese or host a radio program?
My point is, you would live and you would probably even learn how to live happily. Once you can see your way clear through to that, you can probably gain enough perspective to summon the fortitude to get you over and through this very bumpy road on life's path for you. Meanwhile, we are all rooting for you and you don't "have to" have scleroderma to be a member of this forum, giving and receiving support.