What does a temporary relationship break actually mean to a guy? Especially when he says he wants to get back together.

My boyfriend and I were together for around 3 months, but they weren't exactly plain sailing, we're both in uni and our living arrangement meant it was really hard to get together and spend some quality time with each other, and we started dating a little over 2 weeks before our finals, so it meant it was even harder to do anything. we communicated via texts and IM chats constantly, and he was sweet and attentive and loving, and after a month, he said I love you ( I shld say we were very clse friends for a year beforehand) and kept on saying he loved me and never wanted me to leave him etc etc, anyways during finals it turned out we would be in different countries during the summer, and so after a while he suggested we go on a break during that period, and when I brought it up again he said he didn't want to and said if we go on a break it'll equally us breaking up there's no going back.. and then he changed his tune once again in a different convo to we should go on a break JUST for the summer, anyways we went on a break and he promised me he'll "be good" etc and said he would miss me and hated all this, and the terms of the break was when uni starts again we'll get back together and try to make a better go of our relationship. Anyways now I know he's gone back to his ex-gf (who when we were together he said wouldn't leave him alone, and kept on messaging him saying she misses him), and now I feel let down, although there was no 'no other people' clause to our break.. but I'm heartbroken, and I'm contemplating not to get back together with him ever, is this rite? or am I over reacting, and why would he say he loved me and wanted to get back together if he has gone back to his ex.. am I being rational ? he's a very good friend foremost would this ruin our friendship?