Should I take Plan B?

Last night my boyfriend and I had a pretty heavy make out session. We both have pretty high standards for ourselves and both wanted to wait till marriage to have sex (I'm 16 and he is 17). Last night things just got carried away. We both slipped up and decided to rub our "parts" against each other. This happened quite a lot. Somehow we also decided that it would be a good idea to just stick the tip in. We did that and it was enough to make me spot the tinnest little amount of blood. I think he had a little bit of pre cum on him or possibly even cum. Obviously I wasn't not ready for something like that because now I'm stressing out. I'm a very worrisome person so I began to do some research and I know that it is still possible for me to get pregnant. Do you think it is something to be worried about? We can easily go pick up Plan B. I just don't want to do so if it's just me overreacting.