Unprotected sex really scared

So my bf and I didn't have any condoms and he really wanted to do it. The whole time he was telling me he wanted to I was saying my concerns and he kept saying he would pull out. Well I kind of gave in and we had it. But during it he pulled out quick and he did his thing but apparently it was just on my butt. I have a slight feeling it might have dripped onto down there or that he did it a little bit inside but pulled out quick. He kept reassuring me that he didn't do it in me. I'm just really nervous and I'm so stressed out thinking about it. I get my period on the 25th so I have awhile to wait yet to see if anything happens. But because we haven't done this often it was probably our 3rd time but this was the first time ever unprotected, there was a bit of blood in my underwear. I changed my underwear this morning and I went to the bathroom there was a little bit of light brown spotty kind of stuff on my underwear and it was a little wet around it. Today was the first day of Fertility according to this app. I really do not want to be pregnant and do not give me a life lesson I know it was stupid and I should educate ourselves more but I need reassurance somehow that I wont be.