So confused

So I’ve been breastfeeding since my baby was born (Aug 2017). Therefore I haven’t had a period in a year and a half. I know I can still get pregnant but now I have no idea when my window of conception could possibly be.

I did finally have sex since my kid was conceived. It was unprotected (I know, the shame) he did not finish inside of me but I know that also doesn’t matter in the world of conception.

Is there anyway to tell your window of conception when you have no period?

This intercourse was last week but since then I’ve had milky looking discharge that I haven’t had since I was pregnant. It’s usually clear.

Could this be my vagina cleaning itself from the sex?

I’ll use protection from now on, but I just want to be in the clear of pregnancy this time.

If anyone posts any questions I’ll answer them in an edited post because I feel this question may be too stupid for people to know who I am