Crazy Weird

So after I got a negative on Thursday I figured I was out. Then my period didn't start. I just had some spotting. So we went away for the long holiday weekend and I figured I would just enjoy myself and not think about pregnancy, babies, tests, etc.
Well I had more spotting late on Friday night and freaked out that I didn't have any pads or tampons (all but one emergency one I keep in my purse), and would have to get some supplies early the next day when stores opened up. Well the next morning no period. The whole day I was fine. Just a little spotting. And my nipples really hurt. Yesterday I just had a hint of spotting. More sore boobs. And today no spotting. So now I'm back at home. I'm 18DPO. I'm testing with my one and only digital I've been saving for months. If I get a negative that means something is wrong and I have to go to my doctor to start my period or whatever. Or........... I get a positive.