Help!

Alexandria7457

I have been having some irregular periods lately and am not sure what to think of it. My normal cycle is about 27 days and I usually bleed for 2-3 days and spot for 2-1 days after (a total of 4 days every time). Back in April, I got my period and it only lasted for one day and then I spotted one day. It was also considerable light for me, but then again I just ignored it because I have never had a heavy period a day in my life. May rolls around and my period is 4 days late (I track my period on a calender I have always been right on schedule, the 28th day every single time even down to an hour range, early morning, for the last 4-5 years). It is now June and I am a day late, but I figure its only a day, but should I be worried? Could my cycle just be changing itself? (I'm 21 yrs old currently). I have taken two store-brand home pregnancy tests and they both came out negative (one was about 6 months old though) but I'm not sure whether I should take the time and spend money going to the doctor. I'd hate to be in denial and in a few months it turns out I'm actually pregnant and not have known due to faulty tests, but I'm scared to go to the doctor. Also my sister while she was pregnant, she had a period up until her 6th month. I have been experiencing some "pregnant" symptoms, but I also normally have these symptoms when I'm menstruating (morning sickness, bizarre cravings, bloating, strong sensitivity to smells, metallic tastes in my mouth, etc) but it I've been experiencing this recently also when I'm not menstruating so I'm a little confused.