Could I be pregnant?

Rosa • 🐶🐱👨‍👩‍👦‍👦
Okay ladies I need some help. 
According to <a href="https://play.google.com/store/apps/details?id=com.glow.android.eve">Eve</a>, I'm 6 days late for my period (that's 4 period days and 2 regular days). I last had sex on  April 1st and I was ovulating April 2nd-8th. Could I be pregnant? 
Okay, some info: my SO isn't sure if he did accidentally precum inside me but I do remember him pulling out (yes I know, not a great method but it's worked, also idk the feeling of knowing if I was ejaculated into.)
I feel like I'm having all my regular period symptoms minus the bleeding. I have a frequent headache and I've also been waking up feeling like I want to puke but I don't. The feeling stays throughout  the day. (Currently feel this way.)
I'm in school and my 2 current classes have me very stressed. Could my period just me late because I'm stressed? 
I haven't taken a test because the last time my period was late I did take a test and it came back positive and then a few days later I had gotten my period. I was also very stressed around that time. Do you think I should take a test now?
We're not trying to have a baby right now but if i am pregnant we wouldn't be upset. We actually planned to start trying at the end of this year so it would just be a bit earlier and unplanned.
Any advice would be greatly appreciated.