If my blood pressure is 90/52 is that too low?

Depends: There are people who have BP as low as yours for all their lives, and they do fine. If that is a change that you have with medicine, then that is a different issue. What people can't tolerate are sudden changes. It is best to discuss it with your physician.

Depends on baseline: There are some clinical setting where we may worry about lower bp, but in general, lower BP is protective (although people with very low BP may have more of a tendency to feel dizzy). For people who are normally hypertensive, they may not tolerate having their BP lowered that far--it may affect their cerebral blood flow.