What Causes Nausea, Bloating And Frequent Urination?

My last "normal" period was on March 8, 2011. My cyles are usually about 31, 32 days long. April 12, I had an inconclusive HPT, and began spotting lightly, only for a day or two. Then on Thursday April 14 I had major cramps and large blood clots. I've been feeling nauseous, bloated, extremely tired, experiencing frequent urination, shortness of breath, very emotional (a lot more than usual). I think I should be getting a period around the 15th of this month. I'm just not sure if I could be pregnant, or if I should exepect a period, or if what I experienced in April, could have been some sort of implantation bleeding. Any advice?