Hey there! I dont have family or friends support either, so I know where you are coming from.
I started out @ 250. I forced myself to walk three times a week for half an hour. I was thoroughly surprised by the positive side-effects that I didn't see coming. I had this quiet, uninterrupted part of my day where i could reset my brain, feel the sun on my skin, smile, etc. But, at first, I was worried that I looked like a blob walking down the street and people passing in cars would laugh at me. Then a friend told me two things that changed my view and made me face my walks without fear, in fact- i really looked forward to that break from the day.
1. People driving past are lost in their own minds so don't be so focused on yourself that you believe that everyone pays attention to you. They don't care.
2. Even if they do notice you, they aren't seeing you sitting on the couch eating cheetohs and lemon meringue pie- they see you exercising. So the only thing that could possibly go through their mind regarding you is, "good for her."
Cut out soda and sugary drinks, watch how much saturated and trans fat you eat (unsaturated fat is ok) and try to get as much protein as possible. Enjoy taking a stroll a few times a week and eventually you will start taking more because you really want to. That time to yourself is irreplaceable. You're going to love it. Start there.