Hook effect?

So I had a miscarriage back in early August & my period came back normally in October. Well we started trying again and my period was regular, but in December my period didn’t come & I chalked it up to stress & I took pregnancy test and they are CLEARLY negative. We’ll my next period still hasn’t come. I haven’t tested again since my last, but twins run in my family & my husband is a 3rd generation twin. I haven’t gone to my OBGYN yet, but I’m planning to call them this week because it’s getting odd. Any ideas? My period is “irregular” but I think it’s regular just long, more like 5-6 weeks. I’m so confused on what could be going on. This is so odd for my body. Any ideas? Thanks