Hi beth!!!
I'm very similar to you
23, overweight my whole adult life (lucky to be skinny in elementart school though).
Over weightness doesn't exactly run in my family though. Its like there is this great divide... Plump and naturally very skinny. And, the irony is there's two sisters going back to my grandmother. One is always plump, the other super skinny. My grandma's plump, her sister? Skinny. My mom is plump, her sister, skinny. Now there's me and my sister... Guess who's plump and who's skinny XD.
Welcome to the forums and know that you totally got this, I started at the end of November and have lost fifteen pounds up to now!!! (Even through the holidays!!!) Let us know your plan... Me, I count calories and swim regularly.
And since we're both starting young we can have confidence that our bodies will thank us for it. Good luck, I know you'll get where you want to be