My periods are about 52 days apart. when would my fertile most likely be?

Day 38: You ovulate about 2 weeks before the onset of your period, in your case around day 38. You should start trying a 2-3 days before ovulation and continue for 1-2 days afterwards.

May need meds: That is not a normal menstrual cycle and the most likely reason for it is that you are not ovulating. There's a good chance you may need some help ovulating with medicines such as Clomid (clomiphene) or femara. Ask your on/gyn about this.