Am I safe??? Nexplanon question

I had sex a little over a month and a half after I had my Nexplanon inserted. (He was out of the country for awhile). It was withdrawal method (stupid I know). Is it safe to say I'm okay? We have been using condoms ever since then.

Also, My period was a week late already when we had sex and now I haven't had a period for over three weeks. Should I be concerned?