Nexplanon and Unprotected Sex

I’m almost 2 years into my second round of nexplanon and I had unprotected sex the day before yesterday March 25th. He cummed twice, once he pulled out cummed on my stomach and the second time he pulled out and cummed on my stomach and the outside of my vagina. I have very irregular bleeding due to my Implant and my cycles are usually 60-70 days and I’m now on day 64. I’ve been having very bad cramps like period cramps and I’ve been getting that feeling of my period starting like where it starts to get wet down there but it’s just brownish discharge. It feels like my period could come anytime between today and Sunday or Monday. I just want to be sure I’m safe. My doctor tells me that since I have my nexplanon I’m fully protected against pregnancy but I just really want to make sure.