I am quite confident that I am pregnant, but very confused!

I am quite confident that I am pregnant, but am very confused! About three weeks ago I had my period, it was fairly normal, however it came a few days late, at the start of the period I also had a little pink spotting. After my period came and went, lasting about 3-4 days, I continue to feel cramps on and off every day. I have had symptoms of nausea, cravings, cramps, including my in my lower back, bloating, fatigue, headache, fluctuations in body temperature, changes in mood, changes in appetite, heightened sense of smell. I have been on birth control for the past three months, this past month I changed birth controls. I took an in home pregnancy test first in the morning a week ago, the result was negative, two days later I got a blood test, the result was negative. Two days ago I went to the hospital (I'm living in Brazil), and they ran a blood test and pee test, both of which were negative, they say that I am perfectly fine... However my pain so severe that I can barely get up at all during the day, the headache, nausea, and cramps are constant for the whole day. After the first pregnancy blood test I felt very strongly that I was pregnant, or the birth control was causing this. Since the first test I stopped my birth control, this week I started having period like symptoms, but the blood is more like spotting, it is on and off at different times of the day. Today it was a dark brown color. Am I truly not pregnant? I feel like I am, I feel awful, if I am not, what could it possibly be?? Has anyone had a similar issue?