I switched my birth control pill about 6 months ago and the month after I missed my period; which I hear is normal. Then the 2nd month I got my period, 3rd month I got my period but it was extremely light. 4th,5th,and 6th month I didn't get my period. So I stopped taking my pill thinking I would get it; and I haven't gotten it. I am having protected sex now. I have taken about 7 pregnancy tests and there of course negative. I also recently these last 2 weeks have extremely sore nipples. Could I be pregnant?

It's possible... you might have become pregnant any time in the last several months.
Since it has been a few months since your last period, it would be wise to see your doctor. They will do a pregnancy test in the office, but will also likely order a blood test and do an ultrasound to rule out or confirm a pregnancy.

Were your periods irregular before you started birth control? It may be a different pill will be suggested to you. They are frequently used to help regulate cycles.