Could i be pregnant?...i hope:-/?

I had a normal period from Mar.28th- Apr.2nd, then I got another "period" on Apr. 11th and it wasent to light or to heavy and it ended on Apr 16th for just over night then came back on the Apr 17th-23rd, I use a fertility an ovulation calendar and it shows I should have started my cycle again on May 9th. Today is May 27th. I sometimes get these fluttery feelings in my stomach and sometimes I feel blooded, iv been experiencing some lower abdominal pains, iv been craving chocolate non-stop, and I feel as if I'm constantly using having to pee. Iv taken a HPT every month for the last 4 months and its always been a negative, according to my fertility and ovulation calender iv had sex on the days I'm ovulating and on my fertility days. I'm just confused that the test could be wrong and I really could be pregnant as to why I haven't had my period this month.and this months almost over. I just can't seem to find my answers anywhere, can someone please help?