What Causes Delayed Periods And Stomach Contractions With Mood Swings And Tiredness?

I am a 38 year old woman, who has had my tubes tied for 7 years now. I have had regular/heavy periods ever since this procedure. in the last two month, my periods have been two weeks late and the last one was much lighter and didnt last as long. I have been having what I would say are contractions( having 5 kids, i know what they feel like) they can be light or intense this has been going on two weeks now. I felt flutter like movements last week and this weekend they have been more noticable. I did take a pregnancy test in the evening and it said negative and than two days later took one early in the morning and there was a very light postive sign. I feel pregnant, breast are tender, mood swings,tiredness and i feel pressure in my pelvis. Im afraid to go to a doctor, because I dont want to waste anyones time. Could I really be pregnant? or is it something else. And if it is why do I feel movement. Could it just be gas? but would it last this long?please help me. Thank You