idk if it’s possible

so i am 19 years old and i have been on thyroid medication since i was 11 and i have had my period since i was 9 and they were never regular, even when i was one birth control. i got off birth control in february and my boyfriend and i have been having a lot of sex and i’m sure it’s possible i could get pregnant. i just want to know how long after my period i should test, i had a period in march a little over a month after i got off BC and now i’m just wondering will i get one or not. even though there is a possibility i could be pregnant. i know this doesn’t make a whole lot of sense but i hope maybe someone will understand what i am trying to say.