You have to believe in yourself. If you passed the Nclex exam, you can calculate math. The nursing math is really not that hard if you have the confidence. If you believe you are going to make mistakes, you will because you have already tell yourself that. You have to break out of the fear.
Meditate on this scripture: Roman 8:15For you did not receive a spirit that makes you a slave again to fear, but you received the Spirit of sonship.[
a] And by him we cry, "Abba,
Fear stifles our capacity to think clearly and rationally, thus affecting our behavior.
Fear leads to indecision. We are afraid to make decisions for ourselves or others. Such indecision creates constant anxiety.
Fear diminishes our capacity to achieve. We cease trying to accomplish certain goals due to our fears. We become increasingly unproductive as our fears increase.
Fear can cause panic. We suffer from anxiety attacks and other debilitating emotional upsets. We live in inner turmoil.
Fear fosters torment. Emotional storms brew within. Peace and joy are seldom experienced.
Fear damages our relationships with others. We are afraid to be around other people. Perhaps you have been divorced and do not want to be hurt again.
Fear damages our relationship with God. We feel uncomfortable in God's presence, perhaps sensing that He is displeased with us for yielding so consistently to our fears. We do not enter His presence with thanksgiving and praise. Worship is rarely practiced.
I think you are an intelligent person. You just have to deal with fear of medication calculation. Just pray every morning before you go to work to ask God to guide you through each day. You can do it!