Little, I also think that whilst your worst time might be now - your BF being all loved up with his new GF - his worst time may well be later. Later, you'll have processed everything and moved forwards in whatever way, knowing you were faithful, did your best etc. and hopefully being in a healthy relationship with someone, or maybe just with yourself.
His 'new' R will in all likelihood come to an end, as it formed on shaky foundations. It may well be a bitter end because lessons won't have been learned. And he has to deal with the fact that he was an unfaithful partner and he walked out without sticking at things and trying to make them work.
I know who I would rather be in three years time....
T 13 M 7 Me 48 H 46 SS 15 BD 7.14 PA D final 5.16 (H filed)
We receive & we lose, and must try to achieve gratitude & embrace with whole hearts whatever of life that remains after the losses - Dubus