Find a corner where you can put your back to the wall, so no one can take peeks over your shoulder.
Put on some earbuds with your favorite music so you can't hear them chewing. Or earplugs if you'd rather have silence.
Try to have a temporary wall, plant or something in direct view of others if you find their movement distracting.
Have scheduled 'drawing times' so family knows not to interrupt you. Place a sign that says "I'm focusing, please talk to me later." Let them know at this time they should only contact you during emergencies.
If that doesn't work...
Go to your local library to draw pre-sketches on paper. You get the advantage of having dozens of art reference books at your fingertips.
Go to your local coffee/tea shop and draw there during slow times. Buy a drink and sip it slowly. The staff likely won't bother you on down times and you could always sketch your surroundings.
A local mall's cafeteria is another place. It's loud but you can wear earbuds/plugs to cut out the distracting sound.
With this method, you can get half your drawing practice done away from home and when you get some good sketches you can re-draw at home on your PS.
When I was living home I shared a room with my sister... And there was my very nosy mum who used to take a peek at what I'm doing at least 5 times a day. To shut everything out I bought good headphones and listened to music. it does help. You forget about poeple around you. Maybe that works for you too?
find a park, lay out a blanket and buy some noise cancelling head phones (like the $16 skull candy ear buds/head phones....if listening to music helps then play something quiet and soothing) of course when it's winter this doesnt help but hey, then just go with the noise cancelling head phones...sometimes i go to a community library--those always work really well for me. maybe these could work for you too?
Umm, make a couch fort? I know it's kind of childish, but if the problem is that severe it's better to start drawing something that you can finish, than to draw nothing at all.
But, really, the solution here is to deal with the cause of your insecurity rather than trying to avoid it. At some point you're going to want to show people in person what you're doing, and if you haven't dealt with the insecurity there's no way that they can accept what you're doing. Who knows, it might even be good.