I used to be regular on my period but...

I used to be regular on my period but ever since December 2018 my period have been irregular like it would skip a month and would think I’m pregnant but it would come after a whole month of no period. Been ttc for 4 months now and those 4 months I only got my period twice. Like how it’s every other month I get my period. I’m a week late so I’m guessing I’m gonna skip March and it would come in April. Why is this? Could my body be trying to adjust with all the conception .... ? Anybody else had this experience?