issues with enchantments

[excaliburst09]

I enchanted my diamond bow with power 1, and I tried to add enchantments to it, mending and infinity, I tried them one by one with power but it seems like my bow cant add another enchantment

[excaliburst09]

Update, I disenchanted it and found out that I wasn't able to add enchantments by book on the anvil. But I put the base bow in the enchantment table and the only options I found were all power. I was able to stack power, but also not able to add mending. It's weird because my copper bow has infinity and flame on it.