I'm deeply sorry that you are in this situation. No one can tell you what to do, this is your decision and only you can make the call on what you will do.
However I can tell you that if you have an abortion you will probably regret it for years to come. Especially, in your circumstance when you already have one child. As you will know first hand that you are missing out on the joy that comes with having a child. Yes, there is a lot of headaches with childrearing, but the joy far out weighs the headaches!
As well as the emotional turmoil that comes with abortion there also comes a physical risk of complications such as hemorrhage, sepsis, infection, perforation of the cervix, scarring, increased risk of uterine and breast cancer because of hormone shock!
They may or may not warn you of the above known complications that can occur during and after an abortion. In my case they didn't. I regret having the abortion, because I now realize there are many other ways to deal with a "tricky" situation and unplanned pregnancy. I too, was lied to and told the story of sterilization! It's frustrating and I totally sympathize with you. I wish I could give you a hug!
Do you have family or friends around that would encourage you, and help out if necessary?
Make sure that you don't just take someone's advice and do what they tell you. Make sure you research all your options thoroughly!