I have questions- please no hate!!

Madeleine • 21, just here to keep track of all the things, y`know?☺️💕💕
Okay, so these questions might sound a little stupid, but I'm hoping people will be nice enough not to call me an idiot, or tell me if I don't know the answer I shouldn't be having sex. 
Basically, my first question is, how soon after your period is late should you be worrying about taking a pregnancy test
My second question is what happens to the baby if before you realise you're pregnant, you go to a party and drink alcohol
Also, how long is it before an abortion has to be an operation? 
Thank you in advance! 
FYI, I'm 18, I had unprotected sex with my boyfriend about 3 weeks ago, he pulled out, but now my period, according to eve, is late by a day so far. I live in the UK, and got my exam results two days after the unprotected sex, so I don't know if the stress and then relief at getting into university is what's delaying my period. 

Glow Resources

Let’s Glow

Glow is here for you on your path to pregnancy

Glow helps you navigate your fertility journey with smart tools, personalized insights, and guidance from medical experts who understand what matters most.

25+ million

Users

4.8 stars

200k+ app ratings

20+

Medical advisors