I've noticed that when I am really depressed or having a hard time, I always assume the worst from others and "personalize" everything. Your boss just may be really worried about you and does not know or is afraid to talk to you about it... Especially since you had said that the two of you used to be close. To say that he suddenly is a jerk since going on FMLA may just be an assumption. I know because I am guilty of doing this like this all the time.