Hello, I'm 18 years old .
Me & my boyfriend who is 21 have been dating for almost 3 years now, had sex this past month without a condom. My last period started on nov 30, ended on dec 4. We had sex on the 6th than twice on the 13 right after each other, than again twice on the 19th. All times he cummed but "pulled out" before. On the days we had sex twice they were right after each other, which he says may cause a bigger chance of me becoming pregnant due to pre . I am supposed to get my next period on the 28th of dec.
But is there a chance I could be pregnant ?
Please help.

Yes, very good chance, I will assume you are trying to get pregnant ?

There is plenty of sperm in the "pre" fluid, so even once will do the job.

There is no way at all that you can tell at this point and time, you will have to wait for the next period and see if it comes or not.