Your error with the drip is an error of distraction, which is understandable (but not okay) under the circumstances you describe. Two nurses for 14 beds, some of which are new patients who will have urgent medical needs doesn't sound great.
Just the same, you have to prioritize with that in mind so that you can be mindful when administering medications. When you are doing a high-risk task such as medication preparation/administration, you must be able to concentrate fully on that task at hand and for that two minutes (or whatever) not allow yourself to worry about what else needs to be done. I would say you were fairly distracted if your brain didn't tip you off that you had a bag in your hand that was twice as big as what you needed. KWIM? Programming the pump was a second chance to glance at the bag again and enter the correct volume information into the pump or redo using the appropriate bag.
Take some time to review your basic plan/approach. Make some tweaks in how you might be able to plan differently in order to feel less pressured when doing high-risk tasks. Then, as best you can, put this behind you so that stress-error-more stress-more errors doesn't become a cycle. Shore up your plan, recommit to being mindful, then go for it/make it happen.