Welcome here..I am Oluwa...
Your symptoms make sense and do correlate with a Lupus diagnose.
For Lupus...C3 is an indicator of inflammation and activity of Lupus...the following is from lupus.org....
Complement is the name of a group of proteins that protect the body against infections. They work by strengthening the body’s immune reactions. Complement proteins are used up by the inflammation caused by lupus, which is why people with inflammation due to active lupus often have low complement levels. There are nine protein groups of complement, so complement is identified by the letter C and the numbers 1 through 9. The most common complement tests are CH50, C3, and C4. CH50 measures the overall function of complement in the blood. Low levels of C3 or C4 may indicate active lupus.
It is okay to look fine and not feel well inside. It is okay if no one understands that...because really, I don't think they could because they don't have Lupus.
You know you are not a hypochondriac...we know you are not. Your doctors know you are not...you have a small arsenal of pills to proof it.
Who are these people that doubt you? Is it really important that they believe you? Sometimes it is easier, for me at least, to understand the fact, that people, family, friends will not understand us with this disease because they don't have it to experience it. They can have empathy for us..but understanding...humm that is hard to come by for many of us...With that thought, it takes a load a stress off of me.