It is not your fault. It is probably positive qualities about you as a person that kept you with him so long - being empathetic, caring, loyal, etc. He exploited those good qualities.

Reconnecting with friends and families and exploring your own interests and hobbies are great ways to start feeling a little better about life and yourself. If you have any access to counseling or therapy, consider taking advantage of that. Eighteen is a a transitional time, I am guessing you are recently out of high school, are you planning to work and/or go to school? It's a great time for a fresh start. Also, don't let yourself get sucked in if he comes crawling back and tries to contact you again.

I know it is hard to trust again, but you can. Just give yourself a lot of time before you start dating again. In my case, I really needed a few years after leaving a 7 year marriage. I have been lucky to find a new partner who is consistently loving and supportive, but entering a relationship while still dealing with those issues has occassionally weighed heavy on the relationship. I think the key there is just giving yourself time, and also equipping yourself with knowledge so you can watch for red flags in the future (for instance, being able to tell the difference between love bombing and typical new-relationship-infatuation/honeymoon phase stuff).

The road to recovery is long and hard, but you can make it. It does get better!