Why does it seem so hard to get pregnant again after having a miscarriage?

Here is a little history:

I have 4 kids

Two (14&15 years old) from previous relationship

And two (almost 2 & a 3 year old) with my husband

We have been trying to conceive baby#3 since March 2019

I had a blighted ovum in April with a d&ç

Then a miscarriage in August 💔😢

We've been trying ever since with no luck .

From late August to October I did opks and still nothing so I gave up. All I want is a healthy little blessing.

I've also opted to try preseed this cycle

AF is due next Wednesday

I don't know what else to try or if I should schedule a doctor's appointment to discuss what to do next .

Let me add that I'm almost 36 and my husband is 41

Any advice is appreciated