Infertility after a miscarriage?

When I was 17 I got pregnant unexpectedly with my boyfriend. A couple months later I had a miscarriage and after that everything just went out of wack. We immediately started to try to get pregnant again. Right after my miscarriage I didn’t have a period for about a month and when I got my period, it was 28 days long! The next month I had 3 periods.. all averaged about 3-4 days long. After that my period were kinda normal but I ended up not having a period at all about 2 months ago but I kept getting negative pregnancy test... we have been trying for over a year now. Does anyone know what could be going on?