What the hecks going on?

So 2 weeks ago I switched my birth control. Dr said to just start the new pack even I finish the other. So started the new pack and at the end of my period when it was light it started back full force. Called dr office and they said that could happen with the change. Well past few days I've been spotting a little bit and last night and today I've had pains in my right side ovary area. No clue what could be happening. Anyone have an experience like this?