I never had sex but I was hanging with a guy and he touched himself and he had precum and then fingered me. 4 days later my period came (on the correct date) but I spent those 4 days worried and got nausia a lot. Therefore I think that it was because I was worried as it stopped when my period came. The period lasted 4-5 days and after it lasted I started to worry a bit again and sort of felt naused but not a lot. 3 weeks later my 2nd period came and lasted 4-5 days as well. I thought that I was sure not pregnant and the pain stopped but now I am feeling the area between my ribs hurting a lot. Could it be because of stress? What should I do? Because I am afraid to buy a pregnancy test because I am still young and embarrassed that the person with the counter may think that I am a sl*t :(

It is VERY unlikely that you're not pregnant from these circumstances. Especially since you have had 2 periods. You are probably stressing yourself out. But use this as a lesson. Don't get yourself into a situation where you think you could get pregnant if you're not ready to be a mother.