Light Spotting, Variable Pregnancy Test Results. Painful Breasts, Nausea. Pregnant?

i there! I know this is going to sound completely ignorant, but please mind that i'm new to this whole pregnancy thing.... I had two very light periods in , april and may, i'm not even sure if I can call it a period, just light spotting, around the time i should of had my period. I went to the drs in april and took a pregnancy test that came out negative, now after my so called "period" in may, it lasted like two days, and just really light spotting (i'm usually a full 7 day cycle, i'm clock work) so yesterday I took a pregnancy test, and I saw a faint, but very noticeable line on the positive side, so I took another one this morning, and saw the same thing, this time the line a little darker. The last time I had sex was mid march. I'm just thrown off with the test coming up negative at the drs, and now I'm seeing two faint positives? Does this mean I am pregnant. I haven't had any symptoms, expect the past month I gained close to 10 lbs, and more recently I am so nauseated, the smell of most food makes me feel sick, and my breasts have a throbbing pain... I'm just worried because I was told I wasn't pregnant, and unfortunately I am a smoker.. help please! !