Could I still be pregnant?

My periods are normally very regular. Well I was about a week late and was pretty sure I was pregnant. Then I started so I just assumed it was a miscarriage (this period started off kind of heavy but then ended up being really spotty and brownish but that lasted a lot longer than a normal period, like 10 days). About a week later I had terrible cramps, I mean awful! I just figured it was a part of the whole miscarriage thing. Well since then i have had what seemed like 2 periods. 1 was later than it would've been (like at day 30 when I'm normally 26) and the other was at day 20 and a couple of days here and there throughout the "cycle" I would spot. If I was still pregnant I would be 17-18 weeks. I took a pregnancy test at like 13 weeks and it was negative. The only symptoms I've experienced is slight nausea, dizziness, some headaches, twinge feelings in my stomach (almost like small muscle spasms i guess), every now and then some very mild cramps, and especially in the last few weeks extreme hunger! I know it's weird but I just feel pregnant. I guess if I was I would be showing, the only difference in my stomach is a very slight bulge below my belly button (almost like when you have to pee really bad and you've got a slight pooch because of it!), which I guess could just be bloating or something. All of this seems like nothing but I just didn't know if it was possible and if I should go get it checked out since it's so out of the normal for me.