What is "Mavligisi [Alai Yagon]"?
Rashi: This is like Havlagasi (my self-restraint); it is a noun.
Radak: This is strengthening, like "v'Avligah Me'at" (Iyov 10:20). R. Yonah said that the word combines the masculine (Mavligi) and the feminine (Mavligasi). Men and woman try to strengthen me - I cannot be strengthened, for my heart mourns.
Radak citing his brother R. Moshe: The word is Mavligis (like Marbis) with the suffix Yud. The Navi says, I want to overpower my agony, but I cannot.
Malbim: The nation says, now I see that agony is overpowering me.
Why did he say "Alai Libi Davai"?
Rashi: My heart is faint over the Nevu'os revealed to me of coming punishments.
Radak: My affliction is greater than that of Yisrael, for I rebuke them and they do not heed me. This is why it says "Alai".
Malbim: I thought that there is hope, because I am like a Choleh; the illness affects his heart, and he does not feel his illness at all. This shows that the he lost his senses, and the illness reached his Nefesh!