I am so sorry you are going through this tough time alone. Unfortunately you will just have to hang in there until you see the neurologist. Even if you are going because your MRI showed lesions, you will still have to go through more tests before a definitive diagnosis can be made. Just remember, the thought of MS can be scary, but for many people it is a disease that slowly progresses over time. That means that you still have time to raise your girls and figure things out, it's just going to take a little more effort.
I can sympathize with your situation, in fact our situations somewhat mirror each other. I have been diagnosed with MS, and am now beeing seen by a rheumatologist who thinks that I may have fibro, and my mom also has fibro. I am not a single mother, but my husband is in the military and travels quite a bit, leaving me with our four kids to take care of.
This is a rough road, but you can do it. Try to look for the positive things in your life, though they may seem few right now, and don't let yourself get discouraged by the 'what ifs.'
P.S. This forum isn't as active as the Fibro one, so you may have to wait a day or two before receiving a response.
Be joyful in hope, patient in affliction, faithful in prayer (Romans 12:12).