pregnancy after tubal ligation?

Back in Dec./09 my period was late so I took a pregnancy test and it appeared to come out positive, I was shocked, so I waited a few days and tested again and that one was neg. Then Jan./10 rolled around and I had a period (not like my usual ones, absolutely no pain and I always get excruciating pain and it only lasted 3 days compared to the usual 5) Then Feb./10 I expected my period around the 21st but didn't get until Mar.4th which during that time I became extremely moody, nauseous, had heartburn etc... which is pretty common for me before my period but 4 days after getting my period (was very light, no pain again and only lasted 3 days) I started to lactate (which was exactly what happen when I was pregnant with my daughter). So here I am Still lactating, have gain about 15 pounds since the beginning of Feb./10 and have this very unusual craving for gummy worms (I usually don't like candy of any sorts.) Home pregnancy tests come up neg. (I have 2 children and hpt tests came up neg. with them as well, had to confirm with a blood test). Does anyone have any thoughts on what might be going on? (I am a 27 year old female who is otherwise pretty healthy) ????