changing BC pill, help

I was perfectly regulated over the summer then my doctor changed my birth control pill due to bad cramps. From doing that, I haven't had my last period since September. No I'm not pregnant, trust me I've bought many tests to confirm. But then she switch the pill over again last month and I'm not sorta getting my period. Can anybody else relate to irregular period?? I'm spotting but it's not actually bleeding, and I have all the usual symptoms of cramps and mood swings.