Has anyone struggled with secondary infertility?

I have 2 children who are 14 months apart. I was able to get pregnant very quickly with both of those pregnancies. They are now 3 and 4. Since then I have had an early miscarriage (6 weeks) and a late term miscarriage (18 weeks). My late term miscarriage happened the week before Christmas and we have been trying to conceive since with no luck. It turns out I’m not ovulating and have very low progesterone so my doctor is putting me on letrozole to help boost my ovulation. I’m nervous about taking meds and curious to know if anyone has struggled with this/had any success with letrozole that would give me hope.