It sounds like your ex is trying to lead you on. Friends with benefits, but she's engaged? Don't stand for that. Have some respect for yourself,
and don't let her throw your pride out the door. I know you feel heartbroken, but..She's not the one for you. Let her go and be with the guy who makes her happy, and you need to get out there, and do what makes you happy. There IS life after your "first love." My boyfriend lived with me for 14 months, and we had a child together. He and I split in 2007, and I thought my life was over. I laid on the couch for a month before I finally decided to live my life to the fullest. I started hanging out with my friends, and dating other guys. All it takes is a little strength, courage, and faith in God. I know your heart feels crushed right now, but you have to believe that it'll get better. Give it time.
I think you should cut all ties with your ex. Don't call her, text her, answer her calls, take the pictures down, etc. Don't go see her. Do things you enjoy, and spend time with your friends, to get your mind off of her. Don't let her play with your heart that way, because chances are, she isn't coming back, and that's something you need to accept and go on with. I believe the point of a first love is to lose it and learn from it.
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well-behaved women rarely make history.♥