Well my boyfriend has two kids so I know it's not his. This would be my first tho.
A prenatal vitamin will help your body prepare for pregnancy, so will eating well and exercising regularly. If your cycles are irregular then it would be worth buying some ovulation test strips which help to tell you when your hormones are changing and getting ready to ovulate, you can get cheap ones on eBay or amazon.
Having sex every 2nd day from day 10 of your cycle will help to cover your fertile days (day 1 is the first day of your period).
A sperm test might also be worth looking into as you have been trying for so long without any luck.