How Can Amenorrhea With Erratic Eating Be Treated?

I am 19 years old and I have only had 2 periods in the past 2 years. One being from stopping a birth control that I tried for 2 weeks and did not like, I used to be anorexic and this is why I lost my period to begin with but now I am a very healthy weight and have still not gotten my period back. My eating is still very erratic. I could eat a lot one day and barely eat enough the next which I think might contribute to it. I'm really scared because I feel like I won't be able to have children. I used to have a normal period before I lost all of the weight and now I feel like I'm running out of time. Will I be able to have children one day? and how can I get my period back?