I don't know what to think

Yisselt
Hey dearest!!!!
I started to look for my first baby and by fallowing some app I tried to have sex with my husband on my fertiles days, the thing is after 3 weeks I feel those symptoms when my period is about to come. I don't know if is because I'm getting my period or because I'm pregnant. I did the pregnancy test but it was negative, it made me feel really sad, but I thought that maybe was to soon. This is harder than I thought.