Hi i am 18 about to be 19 this friday, last month my period came at 26 days instead of the normal 31 days, and yes it was my actual period, it lasted 6 days...So i waited until the last day of my cycle and took a first response pregnancy test just because my period came early, (it came with 2 in the box, one regular and one digital) both where negative... But i have this firmness on only the left side of my stomach, right under my rib cage... Should i be worried?