Could i be pregnant?

Okay so I got the nexplanon implant back in September. My doctor told me it will make my periods on and off (which it has) she also told me I wouldn’t ovulate and that I shouldn’t have anymore discharge. Well the discharge never stopped. I still do that.

Well Saturday I had sex without and condom and he finished inside of me.

Should I be worried? I’m only 18 and not completely educated on how all of this works so please be kind!