period/cant get pregnant

Tia
Hello guys!
I've turned 18 a few months ago and ever since I started my period I have never had them monthly. They will be every 2-3 months but now I'm trying to get pregnant with a partner i have been with for a while now and we've had no luck. We've tired for months now or even over a year and nothing is happening. 
Can  someone please help me?