Confused

My last period was 1-2-11. I had unprotected sex throughout the month even on ovulation days. My period should have started 1-30. on 2-2 I had brown spotting for 4 days. I only had to use 2 tampons the whole 4 days the rest was panty liners. My normal periods are 3 days heavy. I took a home test on Sunday.To me it looked negative. A friend said she saw a faint positive line on it, just very light. Monday I went to the doc. Their pee test said negative and to consider the spotting as my period, but to watch for my next one also. I had alot of the symptoms to start with. The ones that are recognizable now are sore lower back, sleepy, bloating and a sort of 'full' feeling, but it also felt like I was going to start bleeding today??? I'm very confused and would like to know some opinions. Thank you.