Irregular cycle.... very confused. Could I be pregnant?

Hi all! I’ll try to make this as easy to read as possible. So my cycle has always been very irregular. It’s not unusual for me to go up to 5 months without having a period. This year it *seems* as though after having been on BC for 2 years and then having no period for over a year, I am starting to “regulate” with a period every 2-3 months on the 3rd or 4th of the month. (February 3rd, May 4th, September 4th.) which would mean that I ovulated between the 19th and 21st on the month before. DF and I BD on September 19. Only 5 days later I had 4 straight days of nausea which went away but has now returned and breasts have been oddly itchy. I’m wondering should I test and if so, when? Since my cycle is so irregular I’m not even sure if I did ovulate this month or not. Has anyone else experienced this and turned out pregnant? Thanks in advanced!