I'm sorry but I totally disagree with King Pieb. It may be your body, sure, but it's his child.
Men never get a fair say when it comes to abortions. It's always the woman's decision, and people going on about 'it's the woman's decision', but it's not just the woman's child, it's the man's child too.
I understand that you don't feel ready to have another baby, but as far as your partner is concerned, you are killing his child. I wouldn't stand for anybody killing my child if it were me, so you cannot possibly expect him to just accept you having an abortion.
If you have the abortion, you'll be saving yourself from putting yourself through another childbirth, but your partner will have to live for the rest of his life knowing that you killed his child.
I know you may not see it as a child at the moment, seen as how it's only 7 weeks, a lot of people don't think that life begins that early. But obviously your partner feels more strongly about it, so to him, he probably does see it as his child already.
If you didn't want another child why couldn't you have been more careful? You've got two children already, so no silly excuses about not knowing what you were doing.
I can't help you out on this one, because I would take exactly the same stance as your partner if I were him. How about you try and see things from his point of view.