Well, using withdrawal means there is a chance every time you have sex that you could get pregnant. This is because he could already have sperm in his urethra before inserting the penis into you, and it would come into your body via pre-ejaculatory fluid whether he ejaculates inside your reproductive tract or not. This means if you do get pregnant, you really could not pinpoint last night as being when it happened for sure. Possibly it would be a good idea to go to Planned Parenthood and listen to their descriptions of the human body and contraception before you have sex again. It doesn't sound like what you have been doing is protective against pregnancy in general, whether your boyfriend had a lapse last night or not.
Yes, I agree. Withdrawal doesn't really prevent pregnancy and you've been lucky thus far to not get pregnant. The penis will emit small amounts of sperm when inside your vagina and it's enough to get someone pregnant. As to his climaxing fully inside of you, obviously that increases the risk even more. Your choice is to consider emergency contraceptive pill if it is within 72 hours from the event. Otherwise, at 2.5 weeks after this happened, you can get an accurate result to know if you got pregnant from this or not. Another thing that helps to know is where you are at in your cycle. There are 'more' fertile days than others. The way you figure out a cycle is to start with the first day of your last period. That is cycle day one. And you count from there. About what day were you on when this happened? That info would help us in helping you. :>))