Struggling to conceive 3rd baby

I feel really selfish even saying those words "struggling to conceive" as I already have two kids :(

my first daughter is 7 from a previous relationship and my second daughter is 18 months and has various medical conditions diagnosed at our 20 week scan! I got pregnancy again last may but miscarried at 12 weeks.

I've been trying to conceive since December but just not having any luck. I feel so selfish moaning about not being able to co drive when I already have children but I'd never actually "tried before" and it's taking it toll on me mentally. I feel like I've become

Obsessed😢

Is it completely and utterly selfish of me to feel this way?