选择felt.
feel表示“感受到,觉得”时是个系动词或者及物动词,可以有进行时的用法.
再如：He's feeling guilty for not writing her back.（he's= he is,guilty 表示愧疚的意思）
如果这句话后半部分那个all位置对一点的话,其实用we were all feeling tired but happy 也未尝不可.
这题莫非出题人要考一下all在于助动词与实意动词的搭配位置,简单记为“实前助后”,即位于助动词后,实意动词前.再如They could all go to swim.