Hello. I am 15 and I actually am still a virgin. I know my girlfriend is still one also, and I know she wouldn't lie about that to me, we have been going out for a while now. We normally do things like make out, but thats basically it.
One specific day we did make out in our underwear, but that is why I'm a bit paranoid. She was on top of me and I felt like i ejaculated a bit. I did not enter her vagina at all though, and I am pretty sure of it.
It's been 2 weeks since then and she has been getting unusual symptoms that sort of gave me the conclusion that there was a possibility that she is pregnant.

Symptoms:
Cramps
Headaches
Throwing up in the morning
Frequent urination (although it does seem routine, around the same time everyday)
Craving for foods that she would normally crave on her period

I can only name these based on what she says to me or what I see her do though. I don't know if she is or is not, because some of the symptoms seem a bit abnormal to me, so I'm kind of scared of the outcome.

I am a pretty stressful person, with too much stress at this age. Family is most likely not going to help me, but if the conclusion comes I wish not to have abortion as an option.

So, what I ask is, how can there be a sure explanation for me, and if it leads to me needing to buy a pregnancy test, what's a good excuse I can have to buy one (I'm kind of a shy person, I even feel awkward around those areas of stores), and if true, how can I tell my parents or how can she tell her parents (and to add to that, my mom has walked in on me making out with her with her on top of me once and she claimed we were having sex).