Our final exam has us work in pairs. I am struggling with personal issues and worried about being able to pull my weight. Should I ask to work alone?
It is possible that there are an odd number of people in the class and that someone might need to work alone. Put in a request to be considered for solo work, giving your reasons.
But, there is value in joint work and your professor may be depending on this being a valuable lesson for everyone.
And, to be honest, I'd much rather have a partner who was worried they wouldn't be able to do their part than one who wanted a free ride on my hard work.
If you can't make it happen, just do your best. It is all anyone can do, after all.