What Causes Irregular Menstrual Periods With Pregnancy Signs?

Well I have bin getting most of the pregnancy signs such as feeling sick, always tired and sleeping from like 3 in the day after I woke up at 12 until around 11 at night most times. My boobs seem to have gone two or 3 times bigger in the last few weeks with stinging pains in them and soreness at times. I have bin getting shooting pains in me stomach or up me sides and back aches, head aches and me stomache has came out. I also have got too big for some of my clothes and am having cravings for stuff I didn't like. I have come on for two days two months ago I was on light though at the time and missed my period last month and I have come on this month but keep coming off and on all of the time. I have done three pregnancy tests or more and two come back as unknown and the other ones have come up negative I am thinking of going to the doctors but I would rather have some answers before I do so thankyou.