I dont get it...?? why can young teenagers who dont want kids get pregnant and others cant?

I get so mad and frustrated that dum young teenagers who dont even want kids or deserve them get pregnant so quickly. Like they dont have to go to fertility doctors and take medicine and go through all this trouble to try and get pregnant..they get pregnant instantly.im 23 years old and me and my husband have been ttc for 3 years i mean nothing is wrong with us we have gotten tested for everything i had a hsg he got a semen ysis and were both ok. sorry if i sound selfish but people who really want to kids struggle and others that dont want them end up with them.