Why did he say "Hakshivah"?
Malbim: Also when You hear my voice from afar, at the beginning of the Tefilah, answer me.
What is the meaning of "Arid b'Sichi"?
Rashi: I will mourn in my pain. This is like "Zechor Anyi u'Merudi" (Eichah 3:19).
Rashi citing Menachem: "Arid" is an expression of ruling over, like "u'Redu bi'Dgas ha'Yam" (Bereishis 1:28). "Sichi" is an expression of Si'ach (talk), like "l'Mi Si'ach" (Mishlei 23:29).
Radak: Arid is movement and wailing over illness or affliction. The same applies to "v'Hayah Ka'asher Tarid" (Bereishis 27:40).
Malbim: Also when I moan, even though I do not pray, still hearken 1 and answer me.
To my heart's desire.