Trying to conceive

I came off birth control (iud copper) in September 2019 and used the nuva ring until November when we finally made up our mind to start trying to conceive but now it’s been 7 months and I haven’t gotten pregnant which worries me. I’m 28 years old- i have a 13yr old and 4yr old daughter, i was on the iud copper for 8yrs and took it off to have my second child and conceived in 5 months. My period comes every month but always a week or two later than the last month, am i considered irregular? When should I worry about my fertility?