Has anyone had a harder time conceiving after having a child?

I got pregnant in August of 2016 and miscarried in sept 2016

Got pregnant with my daughter December 2016 and gave birth via emergency c section on sept 14, 2016.

Got a period back (breastfeeding) April 1st 2019 and have been actively trying since. Drinking more water, opks, bd every other day etc and nothing has worked so far

It took us 3 cycles to conceive our first two pregnancies and now we’re looking like I’ll start cycle 5 ttc this weekend. It’s really discouraging and idk if there’s anything else we can try and why we haven’t conceived yet