Ttc after mc

Hi all, so I had a miscarriage Feb 12th at 7 weeks. I bled for 7 days and then it stopped. I have been having unprotected sex since then. But I'm unsure of when to expect my next cycle. If it's going on my usual 28 days it would be due tomorrow. I took a FRER yesterday morning and got a bfn
Is there a chance I could still be pregnant but ovulated late due to the mc? How long should I wait for af to show up? 
Thank you all in advance xx