Missed period but not pregnant.

I'm 18, soon to be 19, and my wife and I are actively TTC. Lots of things have been stressing us out such as finding the right donor, having to find another donor after our first one backed out, losing our kit, and now the biggest thing: I have stopped having periods.
​We are incredibly worried because I am 18 years old. I have always had irregular periods. At most a 4 day period on a 30-35 day cycle. However in May, my period was 16 days late, and when I got it it lasted 8 days. Now, a little over 2 months later, I haven't had a period.
​In short, I'm 18, have irregular cycles, am TTC,  bfn, and I haven't had a period since the middle of May. Should I be worried? Any advice?