You said you fell in love with me in about two months, loved me for about a month and then fell out of love with me within the next month. Are you sure you even know what love is?
You don’t have to have cheated on someone to have led them on, but by making promises, big promises that you're not sure you can or even want to keep, that's leading them on. It's making them believe that they are (or were) important to you. That they were significant enough in your life that you wanted to share your dreams with them and envision a future with them.
“I love you” isn’t the only big phrase out there. Every word you say leaves an imprint, whether in someone's heart or mind. The things you say leave a mark on the people with whom you interact with every day. You have to be impeccable with your word.
It's very hurtful knowing that someone can say that they love you one day and then stop loving you the next, even more so when that person says that they've always been one to fight for a relationship, but gave up the minute their relationship with you hit a hurdle. That despite all the things they said: “You’re the best,” “I’ve never felt this way about anyone else,” “I want something real with you,” “I want you forever," they still decided that their relationship with you wasn't worth fighting for.