Thanks for your good advice. I looked up the bow I was using,which is the Swift Bow of the Forest and has a drain endurance of 10 pts, but it also has a fortify marksman, jump 5 pts, and fortify agility 10 pts. And that is constant effect. So I ended up buying a restore endurance spell and enchanting a ring with fortify endurance, and I think that should fix the problem. We'll see. It may conflict with the belt I have to wear while using the Boots of Blinding Speed which has a dispel magic effect, if I remember correctly. But I don't think I'll wear the boots and use the bow at the same time very often, so it may work out.
The Bound Bow sounds great, and I may switch to that too. I am in the process of making large sums of money from Creeper so I can do this. So I'll see what works out better. I have bought the Bound Bow spell already.
Then I will probably either return to the Caldera mines and see if I can be more successful there, or else I will head over to the Azura Shrine for the Azura's Star, which looks like a wonderful gem. Lots to do!!!
See ya, and thanks for the advice, you all!