Chances of getting preg..

A

Its been 3wks since my Mc. I did a test a week and half ago to check levels and it was neg. Now bleeding (bright red period like)/spotting(browny stage)has been on and off. Obvs im yet to have my 1st cyle. Me and oh caved and had sex yesterday. Bleeding again has been on and off today. What are the chances of becoming preg and how and when would i test/date if i was to be if its possible. So confused 🤷‍♀️