Irregular birth control use. Pregnant with implantation bleeding or my period?

I've always used birth control as a way of manipulating my cycle. Like, if I knew I was going camping I would take an extra two weeks of the pill and then have my period when my schedule cleared. So, due to that my period has been pretty irregular. I only recently started having sex with my boyfriend and now that he's gone, I've decided to have my period (First time in three months). But... It's not what I remember. I'm having these weird slight cramps, lower back pain, my boobs have grown and are tender and I'm having a huge aversion to salt (which is something people on their cycle crave). I'm spotting two days after going off the pill, but it's (TMI) kind of clotty/dark and pink. I'm concerned I might be pregnant, are there other explanations?