Hey guys! I’m just genuinely curious, do you know why your periods are irregular?

I had a miscarriage December 2020 and have been ttc for a year now. Before my miscarriage, I at least got a period every month. After the miscarriage, it took me like 4 months to get my period back and since getting it back it just comes and goes, sometimes going 60 days in between. I’m set to have a doctor appointment but I’m just so nervous they’re going to tell me I’m all the sudden infertile when it only took me a few months to get pregnant previously.