Help....do I have to call....would reraising the flop help??

[attetude]

UTG raises 3xbb to 75cents....CO calls....I have 99 in the sb and call....I call here because UTG is a mouse and wouldnt raise here without at least AK....bb calls too. $3 in pot at this point.

Flop is 5s,6d,9d......I check...bb bets $1...UTG calls...CO raises to $7(half of his stack,he has $7 left). pot is $12 and I have $23 in my stack
What is my move here??
CO is a donk and I would not be surprised if he has the 78 str8. I called here hoping to get a call from one of the other 2 players.

bb goes all in ....UTG folds ...CO calls all in.....Both I and CO are covered..I have to call $15 into a $40 pot...Do I call here??
Am I getting odds to call?? I figure I need to get the full house to win. When BB went all-in here(semi loose passive aggressive player)I put him on the str8 and CO call I figured nut flush draw or small set.