Birth Control Pill and Spotting

I've been taking microgestin 1.5/30 for a few months now and even when I take them on time.. I always tend to spot between the 2nd and 3rd week of the pill. I still get a regular period on the 4th week when I don't take anything. Is anyone else experiencing spotting after being on a brand for a few cycles? Did you switch pills? What worked for you and what didn't? I also feel like I'm gaining weight that I can't lose :(