Switching BC

So long story short, I was having trouble with constant periods on Lo Loestrin FE so my doctor switched me to Tri Sprintec. Instead of waiting for first day or whatever you would normally do when starting birth control, she told me to just finish my pack of Lo Loestrin and start my pack of tri sprintec right away. So I did that. But now it's been a month since I've had my period and I'm getting worried. My SO always pulls out. And I always take my pill at the same time or within the same hour. Do you think I should be worried? Or is my body just regulating to the new pill?