Tips??

So I have a two year old son & my pregnancy/delivery with him was perfect. We started trying when he was 18 months and got pregnant the following month. (I was still breastfeeding) that one ended in a chemical. Got the ok to go ahead and try again,. Got pregnant right away.. (I was still breastfeeding) that one ended in a miscarriage. Was told to wait a cycle. I stopped breastfeeding , and nothing. It’s been two cycles, and nothing. Even got my positive opk on the 12 and had sex my whole fertile window. I’m on baby aspirin and I’m taking prenatal vitamins... my question is was I more fertile breastfeeding?? My uterus is healthy and blood work is good. What are some tips I can use to get pregnant?