I just finished taking 3 different prescriptions that have a pregnancy category b rating. How long should I wait before trying to conceive again?

Any Time. Category b is a very safe medication class in pregnancy. Generally, you want to avoid any medications during the first trimester if at all possible, but if you must take something, cat. B is preferable.
Category B. Pregnancy category b drugs are among the ones we believe to be safest when you are pregnant, so it shouldn't be necessary to wait at all.