what should i do?

let start off first like this..i got my period on november 25 and it end on dec the 2..and it was a really heavy period..but now i am three days late..and i took 4 pregnancy test..the first one was slightly positive but you can still see the line so i took another one couple hours later and it was negative..that was a week before i miss my period..so i took two more test yesturday and it did the same thing too..one negative and one positive..i been getting nausea and mood swing but i dont have sorely of breast or anything like that..the only other thing i have it i been eating like crazy..and i havent been late before..my abdomen is getting better..but why my test is messing up..