Wa Alaikkum Asalaam
I'm going to be straight and to the point, if you are still an active member. I don't mean to hurt your feelings but just being honest.
First of all you did not live an life according to Islam, you knew boyfriends are haram yet you went went this man. Secondly, this is normal in a Godless Western life where you are living. You blended in to your non Islamic environment and thought having a boyfriend was normal and this guy knew that he could take you for a ride.
As for feeling love for him and feeling depressed this is a normal teenage reaction to lost love. However, if you had kept to a strictly Islamic way of life then you would have been spared all of this.
Moving forward my advise for you will be to get to know your religion. Pray five times a day at the stipulated times and try to implement the Five Pillars of Islam in your life. Read the Qur'an and the Hadiths and the Seera of the Prophet (SalAllahu Alayhi Wa Sallam). There are plenty of material on the internet particularly Youtube where you can listen to recitations of the Qur'an, if you don't know Arabic then there are translations in English.
I suspect your family does not follow Islam either so try to get them to do these things too.
I always say that the closer you are to Allah Subhana Wa Ta'ala the further away satan is and the closer you are to satan further away Allah Subhana Wa Ta'ala is.
The thing with advises are that you can wither take it or leave it.