I'm Looking Into Restarting Birth Control, I've Been Off It

I'm looking into restarting birth control, I've been off it for about five years, but for a variety of reasons I think its time to start again. Aside from the typical reason, I have been told taking one that is estrogen based will help improve my hereditary hair loss. My only concern is potential side effects, mostly weight gain. It seems like the estrogen based birth controls are the most likely to cause this, is that true? And if so how much weight gain could I expect, and is there a type of estrogen based birth control that is less likely to cause it. I've been on the generic ortho tri cyclen lo before, and I don't THINK it caused me to gain weight, but I am concerned now because I am right in the middle of trying to lose weight and I don't want to stack the deck against myself potentially.