Trying to conceive and frustrated

My husband and I had unprotected sex for four years before we were married. We were using unconventional ways of protection. Then we were "caught" and I got pregnant with our son, and we then got married. Now with my son 3 years old, soon to be 4 years old, we feel that it is time. I am a school teacher, and I wanted to conceive right at the start of the school year. Well last year with no success on that I've given up that wish. Twice I have used those ovulation predictors. Our problem is that with my husband's work schedule we can't always have sex on certain days. Sometimes when I am ovulating or soon to be he may not get in from work till 11:30 at night and has to be back up at 4:00 am. I just wish I could consume my thoughts away from all of this baby business!!! I'm on my period now. Im so frustrated!