Periods

Stacey • 20 year old with daughter at 4:), pregnant with #2
I got my contraceptive implant out Tuesday 25th march and when I was it it I didn't get period regularly I had brown spotting yesterday but nothing since and had sex last night. How am I suppose to know when I'm ovulating? Doctor says u can still ovulate without a period... This is my calender.. Had my period in febuary but not march. It's suppose to be easier to fall pregnant after coming off Thr implant as ur fertility comes back as soon as it's out. Any advice ???