TTC but no period in 4 months

I haven’t had a period in 4 months, me and my partner are TTC but it’s quite difficult when I have no idea what my cycle is. Been to GP who said they aren’t concerned and to come back in 2 months if still no period.. have I got a chance of getting pregnant if we try every 2 days? Or does having no periods mean I’m not ovulating? Tried my first OPK today and was negative.