Oh, sweetheart, please don't beat yourself up so much ... it won't do you a bit of good. It sounds like you've had a really rough time of it in the past and that's tough. And believe me I know how tough it is to try to lose weight, and I totally understand about being embarressed to go places or do things - but here's the thing, you have got to stop letting being embarressed or insecure about how you look stop you from enjoying life or from doing things you want or need to do. We only really have today you know? So not allowing youself to live your life to its fullest potential is such a waste of time. Unfortunatly there will always be people out there who are unkind (in any number of ways) ... but that's their issue, don't let them make it yours.
When I first started trying to lose weight the right way I was terrified of going to work out in a public place. I was certain that everyone would laugh at me or just be plain mean. What I quickly realized is that for the most part, people are so wrapped up in their own thoughts that they're not paying any attention to you. And anyone who actually takes the time out to make some sort of snide comment to you is doing so because they've got issues. Losing weight is difficult enough and involves you dealing with your own issues - there was just no way I was going to take on some rude stranger's issues as well.
I'm not sure what advice to offer you. Be patient with yourself. Losing a significant amount of weight in a healthy way takes time so try not to get discouraged, I promise the exercise gets easier and after a period of time you'll probably even start to enjoy it (working out is my biggest stress reliever and my favorite time of the day - go figure). Eating healthy also gets easier (especially if you avoid temptation
Keep your chin up. Acknowledge that it will take a while to lose the weight, but don't put your life on hold until then. Good luck. Grace