Had boyfriend and I were having sex. For a couple of seconds his penis was in my vagina, but did not ejaculate or have pre-ejaculate. After a while of just making out, he pre-ejaculated a bit but it dried then he put his Penis back in for a little. Sometimes the tip of it would brush up against the entrance. He never finished. After sex I went to the bathroom and got my period 2 days early. Now, my question is that is there a chance that I can be pregnant? If so, what is the chance? Should I buy Plan B? PLEASE HELP!