Annoying symptoms and not pregnant. Anyone else experience this?

Hi everyone,
I stopped taking the pill at the end of November on my gynecologist's advice. Because I had been on the pill for so long, my hormone balance seemed completely off. This made me think I might be pregnant for a bit. After stopping, I felt much better after about a month!
Just for info: my first cycle lasted 36 days.
My first natural period started on January 4th.
I had unprotected sex on February 4th... I thought it was okay because my period wouldn't last much longer... I didn't expect a second cycle to obviously last longer than the first. Oops.. (a baby would be welcome, but not really the right timing)
Eventually, I got my period on February 15th. (Maybe TMI, but: this period lasted long and varied a lot each day between heavy red bleeding without clots and old brown blood.) Naturally, I went to look it up and read about implantation bleeding. It seemed unlikely to me because it wasn't just a few drops like described. But after my period, I still have light period cramps every day. Also, my areolas are swollen, and I thought that would go away after the period. Since the symptoms persisted, I took a pregnancy test this morning, and it was negative.
Now my question... what could this be?
Is this still related to stopping the pill?