do any of you feel like it never going to happen?

cause sometimes I feel that way, cause my bf says he wants us to have more kids...... but then rarely has sex with me, he says cause he don't like breathing hard..... but most ppl feel that way after you have sex....... right! also being 34yrs old you can't tell me that he don't like to have sex. we want more kids but sex twice a month or sometime once isn't going to do it and I'm starting to lose hope 😔😢 anything I can do too get what we want?