Pregnant?!

I've been worrying so much lately I'm pregnant I had unprotected sex the 13th, 14th, and 18th of August. The 13th and 14th my boyfriend finished (not in me he pulled out both times) and on the 18th he didn't finish.

I'm just worried that I might be.. I don't gave any irregular symptoms (some things that are 'pregnancy symptoms' I've always had this time in my cycle so its normal but confusing). My last period was August 4th-9th and on the 18th it was my first day of my fertile window (I didn't check before hand or I wouldn't have had sex because it's easier to get pregnant then).

Basically I'm trying to figure out if I should do a test, and if I do would the results come up if I were pregnant? or should I wait... (I'm super worried I turn 17 tomorrow and um.. I just can't be pregnant it'd be really bad)

Also I've had no 'morning sickness' (I've always gotten a little nauseous randomly bc how little I eat so it's normal for that), I've had tender breasts but I've also started working out recently and that's why I know that, and I've had light cramps I'm guessing because ovulation.