Suggest Precautions To Be Taken After Having Unsafe Sex

Hi, I am 18 years old. Today my boyfriend and I dry humped in his car. He tried to finger me but it hurt really bad so we decided to dry hump. My underwear was already off and he was wearing a condom (in case he came from the handjob- he didnt want to cum all over his car). We did that for a minute and then I decided to put my underwear back on. We noticed that the condom slipped off when I was putting my underwear on. Is there a possibility I got pregnant? he had precum and I don't know when the condom was off when we dry humped. I asked him and he said the middle of his dick was close to my vagine and the tip was on my butt. Should I try to get Plan B?