MS and Lupus? Wtf?

So, this passed summer I was diagnosed, by Neurologist, with MS. But she refused to treat me and insisted I see a MS specialist. In the meantime, I felt tortured. The pain all over my body, the fatigue and the headaches were so severe, I literally cried every day. One day, I go to the ER, I was admitted and saw a neurologist literally for 5 mins. Not sure what he saw in my file but I was released and the very next day, his nurse called me to tell me that this dr who's I saw for 5 min, got me an appointment with Neuro Science dr for the very next day! And it's been insane. All the tests, the scans, the questions, the different combo of meds to see which one worked...insane. But it was also God Sent because after all this time, I had a definite diagnosis of Secondary Progressive MS AND Lupus! So now, I'm getting all my bloodwork and vaccines needed to get ready to start my Rituximab infusion. I'm happy there's a plan but nervous about the side effects. Does anyone know? Or have any idea of what I should expect? Thanks in advance!