Trying to get pregnant

Hey, so I was on depo for about 4 years consistently up until about 2014 I've never been pregnant. Well feb 2015 I received another depo shot because I started having sex unprotectedly again. Well April of 2015 I went to the ER of extreme vaginal bleeding turns out it was a miscarriage which I was about 8weeks. I've been having unprotected sex with my bf since, trying to get pregnant and nothing is working? HELP