Trying to conceive

Hi I’m new here and this is the first time me posting so bare with me. Anyway my husband and I have been trying to conceive our second baby but we are having the worst luck ever and we have been trying for almost a year, the year 2018 I had my first son and he is 19 months old now and I only breastfeed him once daily which is at night time cause he will not give it up at all. So my question is that what is causing us bad luck with trying for another baby and if anyone has any ideas or tricks please let me know thanks