Why Have I Been Experiencing Bloating? Am I Pregnant? Are They Side Effects Of Getting Off Pills?

I went off the pill 5 weeks ago and had a period right away. I am now two days late. For the past few weeks I have been experiencing bloating (this has gotten better this week), dull uterine aches, and now dull pain on my left side and in my back on the left side. I have taken two pregnancy tests and both were negative. I was on the pill for 13 years. Am I pregnant or are these just side effects from going off the pill.