TTC with very irregular periods

We are trying to conceive, just started the third week of sept so hasn’t been long, (with my ex fiancé we tried for months and got no where) but I’m just so worried that it’s not going to work because my periods are very irregular, like one every 3-4 months irregular, they’ve lasted as short as 5 days and as long as an entire month.... I’ve been on birth control and that didn’t help and personally I don’t want to take any form of birth control after my first experience. We are not using any form of protection and we have sex consistently, about 3/4 times a week at least. I’ve also started taking prenatal vitamins and taking ovulation tests every two days. I’ve also taken a pregnancy test within the last three days because according to this app my period is late by 5 days given the information I put into it. Negative pregnancy test and negative on ovulation... someone please tell me that there is a chance because I’m only 22 and all I want is to be a mom..