Will i ever get pregnant.. Feeling a bit useless

I hate this feeling :( i went three days over and now i have light pink spotting so i assume the flow Will come soon. 
​I just feel useless, why can't i get pregnant arena like everyone Does by looking at eachother..
​And My Fiance wants this aswell but he doesn't understand completly why i get so disapointed each month.. 
​Feels like i can't give him a family but the feeling goes away but comes back Every month when af arrives.. 
​don't know what to do, im already in line to get help..any tips ?