Since your husband is supportive then my advice is to keep the baby. Good that he don't mind with having another child but make sure he helps you around now and when the baby is born or whenever you need him to. Your mental health is also very important. Abortion is an easy way out but the guilt is forever. And you may also have difficulties trying for another baby in the future, if you wish to add another one, which happens to many, including my circle of friends. Take extra precautions, a contraceptive, IUD, pills, etc after birth. It will be exhausting having little kids and a baby. I've been there and like you I wasn't ready but I still keep my baby. When they grow up, you'll thank yourself that despite the exhaustion, you are still able to handle and take care of 3 kids and you're glad that you did not follow your heart to terminate your innocent baby.
I feel that if you still get pregnant after taking precautions then maybe you and your husband are meant to have 3 kids. abortion may seems like a better idea for now but the guilt really follows you though out. i understand that it will be very tough on you to look after all 3 but it's not forever. maybe try to get your husband or other family member to help out with kids or chores.
The tiredness and pain during pregnancy and postpartum may seem like forever, but it will be better when they are bigger. Then maybe you tryta take some contraceptive meds recommended by doctor. For now, discuss with husband, support each other and make a wise decision that you wont regret nxt time. A life, is still a life no matter when you terminate the pregnancy.
I think you need to calm down first. think through it on the bright side and do not make regretful decision. at least your hubby is supportive and I hope you stay positive. hugs*
Think positively. When you are strong . You can go through this unexcepted pregnancy. Go to doctor and check your health condition first.