so the situation is :

on December the 5th, my boyfriend fingered me for the first time, im sure he didn't get anything on his fingers. on the 9th however he fingered me again. i was meant to get my period on the 11th of December but it didn't come, im usually quite irregular so i didn't think anything of it, however i began to think i was pregnant..but i got a 5 day period about 3 or so weeks later; however my periods which i have been having for 2 years usually last 7 days. i took a pregnancy test like a week or two after, drank some water about a bottle and it came out negative; did the water dilute the test? can i be safe to say im not pregnant?
on January 20 something, my boyfriend.. i cant remember if he fingered me or not this time.. but once again, its February 17th and i have no period. now i have like some fat around my bellybutton area, is this normal? my breasts are only sore when i like poke them or such i have no morning sickness, nausea etc however i am really paranoid im giving myself symptoms. safe to say im definitely not pregnant? im 16 btw.