Extremely faint positive on EPT pregnancy test which then disappeared..what is going on? PLEASE HELP!?

My boyfriend and I are generally pretty careful when we have sex, but recently we've resorted to the withdrawal method. My period is now 8-9 days late. I've been fatigued, moody, have been urinating more frequently than normal, my breast and nipples are extremely tender and swollen, I am bloated, and I've had a dull ache in my lower back that won't go away along with some slight cramping. Along with being more tired than usual, whenever I lay down to sleep, I cannot seem to fall asleep easily and it is so frustrating! Also, I seem to get very hungry and crave a particular meal (i.e. yesterday it was blackened haddock over caesar salad from my work), but as soon as I cleared my plate, I felt nauseous the rest of the day and I don't even want to look at blackened haddock again! This seems to have been happening more often lately..as I type this I am also feeling rather queasy..so I took two EPT pregnancy tests this morning, the first which came back definitely negative and the second came back with a very faint positive line that stayed for about 3 minutes then disappeared. What is going on?! Any helpful/insightful/experienced advice is greatly appreciated. Thanks! :)