Is there a birth control that doesn t come with weight gain? Thanks?

A diaphragm

yes keeping your legs closed will not cause you to gain weight

The Copper IUD is non-hormonal, so that likely won't cause any weight issues or any hormone issues. It also depends on your body - the arm implant (Nexplanon) for me hasn't made me gain any weight in the 4 years I've had it. My friend was on the depo shot and was fine with it. She then got the implant and gained weight. The pill didn't make her gain weight, but it gave her constant nausea and headaches. You will likely react differently to each type of hormonal contraception. The only one that cannot cause weight gain is the Copper IUD.

Different women react differently to different brands and types.

as does pregnancy

It's only a couple of pounds at most.