Me and boyfriend trying to have a baby together i already got two but it's like we can't have them what could be wrong?

Conception: 20% chance of pregnancy/cycle, infertility is after one year of trying. Sperm survive for 3-7 days, an egg can be fertilized for 24 hours after ovulation( ~1 week/ month). Consider over the counter ovulation testing or temperature charting. Important to relax,limit alcohol,smoking, drugs, hot baths, tight underwear for men,computer on lap/cellphone in pocket(heat,rad affects sperm). Good luck