how long after your miscarriage did you start ttc?

I was just wondering how long after a miscarriage you have to wait to start trying again, I miscarried at 14 weeks, I was in labour and passed the placenta and baby on April 20th I've had my first period and my boyfriend and I started trying again but my cousin that had a miscarriage said you should wait 3 periods after before trying but I was only told after my first period