There's no such thing as an attack of opportunity in this game. Maybe you're confusing it with Neverwinter Nights or Temple of Elemental Evil?

Inceidentally, AD&D 2e doesn't have attacks of opportunity. 3e does, but Icewind Dale 2 does not implement them.

Yeah probably, I've just come back to BG2 after a 3 year lay off & have been playing NWN.

My sorcerer was newly generated so probably around level 9 or so. The problem was I always gave him 3 str because I get the girdle of hill giant strength really fast, but I guess that was causing him to die because of str drain.

If Strength drain is a problem, try casting Strength on the character who keeps dying. Remember, Strength has a long duration, so you can cast it once and expect it to last until you rest.

Sometimes it's easy to overlook that sort of spell, especially when you are used to wearing Strength setting equipment.

If you only need the spell once, remember that you can cast it from a scroll if you are a Sorcerer with (I think) 10 Intelligence or more.

Edit: Or you could use a Potion of Strength.

I just got the message "Don't use missile weapons in close combat, enemies will receive a +4 attack bonus."
That must have been what I was thinking of.