Why am i bleeding on two different brand of pills?

I used microgestin (generic for loestrin fe), for a year and some change. A couple of months ago, I started bleeding for a month. towards the end, I started to feel nauseaous and cramp up very badly (I didn’t have cramps before while on the pill). The doctor changed my birth control to Yas(this will actually be the 2nd time we changed it), and before I started them, the bleeding mysteriously stopped. Literally the same night after I talked to the doctor. I wanted to keep the same pills, but decided it wouldn’t hurt to try out something different as I didn’t want it to happen again. I have been taking Yas for about 3 months now, and last week I started bleeding (I didn’t miss any pills and am not supposed to be on yet-I usually skip the inactive row anyway so that I will not bleed), and it does not seem to be stopping. What should I do? Is it the pills or me? This is such a nuisance!