Who are "Ohavai v'Re'ai"?
Rashi: They seem to me like lovers when they benefit, but when they see that the affliction came to me, they do not stand for me in my difficulty; they do not help me.
Radak: Normally, people full of pain, their lovers and brothers forget them, for they do not want to see their affliction, and distance from them - "Kol Achei Rash Sene'uhu" (Mishlei 19:7).
Why did he say "mi'Neged Nig'i Ya'amodu"?
Rashi: Refer to 38:12:1:1.
Radak: They do not visit me; visiting strengthens the Choleh's Nefesh.
Malbim: A Goses, his friends already despaired of his cure and distanced from him.
Who are "Kerovai"?
Rashi: They show me that they are relatives.
Radak: They are Re'ai (my friends). The matter is repeated in different words. A friend is called Karov, for he is close to his friend in mindset and desire, or if they have business together, of they are neighbors, or relatives.
Malbim: They are those who were always far. Now they are close to me, for now they let everyone approach me. A Mes, his enemies and friends, big and small, gather to him.