Need Advice :(

Im almost on my first year mark in my med-surg career as an RN and ive been feeling so much doubt in myself. I work in a Med/Surg Oncology unit and im currently not chemo certified. Honestly I can say that most days arent bad. Most of the time I only get 3 easy patients not really bad very manageable and sometimes I get bored that I try as much to help other nurses or ask them if I can do something for them like inserting heplocks etc so I can practice my skills. Some days can be tough though, like having neutropenic patients, demanding patients etc.. During this first year ive made these mistakes: 1. Gave a wrong dose of a PO antibiotic 2. Reported a critical lab result to the wrong MD ( pt is newly dx hiv, id fellow informed me of the dx, so i informed him of the critical result, turned out he was out of the hospital when i paged him. should have called primary md. 3. Held a Chemo pill that wasnt supposed to be held ( I investigated why I did and found out that several nurses contributed to the mistake. rn who reviewed chart marked the mar " do not give" but i should have re-checked myself, that was myself ). Being a newer nurse, I dont know if its normal to make mistakes like these. Everyday at work I remind myself that I should be extra careful but still at the end of the shift I always feel like I did something that will bite me in the ass. Im scared to death. Am I just being too hard on myself. Need advice from seasoned nurses.. Thanks!