Please help me with these Magic The Gathering rules?

Ok so here's the deal My green deck played a howl of the night pack (put a 2/2 green wolf counter into play for each forest) so I had 7 2/2's, 2 1/1s and a 2/4 on the field…now my 1/1 had a Lust Of War enchantment on it which makes me lose 3life each time the 1/1 gets tapped and the creature has to atk each turn if able…well I had 3 life left and I used an Overrun which gives all of my creatures +3/3 and trample until end of turn…basically I obliterated him only I had to attack with the 1/1 and lost 3 life…we both lost, how does this work?? Do I lose first because the 3 damage is dealt to me before the end of combat phase? Cuz thats a bad beat. haha