I'm 19 And Had Unprotected Sex With My Boyfriend About

I'm 19 and had unprotected sex with my boyfriend about 4 days ago. He didn't ejaculate, but I have heard that it doesn't matter and that precum can still get me pregnant.
Right after sex I started bleeding and haven't stopped. I think its heavier than what is considered spotting? My period has always been irregular though. With the bleeding I'm getting now is not quite as heavy as my usual period, I am getting slight cramps. Also, I have a very light period about two weeks ago, so I'm very confused at the moment.
I'm stressing and freaking out a lot here and I'd really appreciate some advice, thank you.