plan b after sex

my boyfriend and i had sex on Tuesday. The condom slipped off and got lost inside of my vagina. i went to the bathroom and didn’t feel it so an hour later he fingers me and pulls out the condom that was in me that i couldn’t feel and didn’t know was still in me. I took a plan b on Wednesday the day after we had sex. It is now Thursday and i noticed I had stringy like discharge and it kinda of had a smell to it even tho i showered after sex and i showered this morning. can anyone tell me what this could be because it is not my normal discharge. also i was wondering i can’t be pregnant right because he pulled out and never finished in me. idk i’m not sure if precum can cause pregnancy but i just need some advice.