I don't want to come off preachy and judgmental, but maybe you aren't getting pregnant because God doesn't feel it is the right time for you. Based on your post, if you have broken up and slept with other people, it doesn't sound like the two of you are ready to raise a child together. Sometimes there is no medical explanation for infertility. Sometimes it just isn't the right time.
Different women get m/c. A lady I know she went through 3 before she actually got to carry full term. I would base it on that. Have you been to your ob? You should go.