I'm 16 And My Boyfriend And I Wanted To Try

I'm 16 and my boyfriend and I wanted to try sex, I never done it before and I was scared! He wasn't aroused at all and he only put it in and out as we diddn't have protection and like I said was pretty scared! He diddnt pre-cum and as far as I know even if pre-cum inserts the body it can only make you pregnant If the pre-cum mixes with old sperm but that couldn't of happened because I never had sex before ? I'm so so scared and keep thinking I'm pregnant ? my periods due any day now and I'm stressing out ! could I be pregnant ?