Not consistent

Hello all! I’m 31 years old and we’re TTC our 3rd and last little..1st one was easy to conceive, miscarried the 2nd and 3rd was easy to conceive but now we’ve been trying for a year, with on miscarry right when we started..did anyone’s period change to too inconsistent after 1 or 2 kids, or mayb the older we get, to where it was harder to conceive because the ovulation period was harder to track? I just started taking an over the counter fertility pill, anyone try any other things or fertility pills!?