A little help on how far gone i am please ?

Hi sorry to bug you all agin but i am slightly in a muddle have a bad habit of not taking too much notice in my period lol....My last propper 5/6 day period was on the 13th June and i normaly have around a 28 day cycle however my next period was due 11th of july but i was around 12 or 13 day's late (very very inperculiar as i am always regular like clockwork) But when i did come on it only lasted 3 day's also not right as sometimes i even bleed for the 7 day's and had all the pregnancy symptoms (constipation tired sick feeling) but test was negative.So when my next period was late and never came i done a test and it was positive....any ideas???