When to see a Doctor?

So, Im going to try and make this post as brief as I possibly can. I got pregnant when I was 20 years old and had my son shortly before my 21st bday (year 2012). He is now 6. After I had him, I put myself on the depo shot bc I wasnt ready for a second child. right when my son turned 5 I got myself off of depo and we tried and tried and tried to get pregnant. Well in May 2017 I finally found out I was pregnant. In the begininng of June I woke up with sharp cramps and heavy bleeding... went to hospital and they confirmed I was having a miscsrriage. my question is, I have been trying for over a year.... when should I see a specialist? What type of doctor, obgyn or fertility specialist? Anyone else have a similiar situation?