Anyone know what happened?

I know that there is possibly no answer and this is a bit wordy so please bear with me. For about a month, maybe a little longer, I was spotting, tired, nauseous, and cranky all the time. I took about 5 pregnancy at different times throughout this and they all came back negative. I had an obgyn appointment booked but about a week before I got my period, it was very heavy and one of the most painful I have every had. I told all this to my doctor, she checked me out and told me everything was fine, and put me on birth control. But I'm wondering, has anyone else been through this? Should I get a second opinion?