Me and my girlfriend (both 15) have had sex twice . The first time was fine . The second time we were building up for hours , I occasionally put it inside her with no condom on. I never got deep and it was kinda painful for me . Then I remembered that I had masterbated earlier and didn't really clean up , I couldn't see and semen on my penis and I tried to wipe it off before hand . Now her period is 2/3 days late, should I be worried , she's very stressed due to this situation even though her period has been late for the past few months
There is ALWAYS a risk of pregnancy with any sexual contact. Putting your penis in without a condom can "squeeze" any semen in your urethra out and into her vagina - you did say you'd already masturbated that day.
Always use protection ALL the time. Not only does it reduce the likelihood of pregnancy but it makes sex more enjoyable for both of you when you don't have to worry.
Stress can make her late.
Hope it helps.