Welcome to the forum Koolteach
I'm sorry about your diagnosis which I hope is the right one because an SLE diagnosis is weighty. Please see a rheumatologist who is lupus literate if you haven't done so already, who will investigate the cause of the stomach pains and take care of every aspect of the disease referring to other specialists as necessary. There are several possible reasons for such pains and they should be thoroughly investigated to treat correctly.
I suggest you find out about your lupus, because everybody is slightly differently affected. You can do this by getting test results and learning to understand them. Have a look at the diagnostic tests that should have been done to make sure they have all been done, not forgetting urine. Then start learning about treatment options. It is important to treat the disease itself with disease modifying medications such as Plaquenil, using symptomatic relief on top of that as needed.
Possible physical causes of fatigue need investigating too: simple iron deficiency anemia often goes undiagnosed surprising as that seems. There might be thyroid disease, depression, fibromyalgia. Apart from physical causes, it is very easy to overdo things and to try to maintain pace and performance exactly as it was before, but the body needs rest not stress. There are many aspects to the adaptation business and to developing coping skills.
Bye for now
Clare