Do small things at a time.
For instance, just go outside. That was all I could do at first. When you're feeling a bit stronger, walk out to the end of the driveway, or to the sidewalk. Then eventually challenge yourself to walk to the end of the block, then around the block, etc. To run errands in the meantime, get someone to go with you. Depending on where you live there are support workers through non-profit agencies (also private ones if you've got the money) who can come to your house either as needed or on a regular basis and help you set and achieve goals and accomplish daily tasks, whether it's cleaning your house, grocery shopping, getting to appointments, etc.
Eventually, push yourself to go into places like stores. Make them little trips; don't get too risky if it still freaks you out to the point of triggering you to not want to go out again. In my experience, challenging is good. It's the only way. But you don't want to be a tyrant on yourself and make it so that you never leave the house again. That's usually my philosophy with pretty much everything: if I push myself hard enough I will stop being a loser and start being a better person. (Yeah right, look where that's gotten me...)
Good luck. Hope you're doing alright.