OP, by the way you describe this man, he may not be a shit. He may have been honest about envisioning having children with you... but I suspect his vision was for a later time, not 6 month into a long-distance relationship between 2 people who have recently met, are getting to know each other, fancy each other like mad and still have not got to the point of sorting how this relationship is going to work into the future.
He most likely was counting on seeing how this was going to work. Introduce you to each others' kids in a timely and convenient manner. Decide where you were going to live, whether one of you was going to move into the other's house, buy a home together or continue living separately. See if things work living together.
AND THEN have an adult, responsible talk about having your own children.
Instead, you have dropped a bomb. You falling pregnant basically days after he giddily told you he'd love to "have a little girl with you" right before starting lovemaking was most likely not in his plans, and honestly, wouldn't be in anyone's plans.
Yes, he was stupoid for not ensuring you used contraception. But you were the one with the most to lose, and you were the one who have admitted that planned this.
The minimum this situation would have required was honesty from BOTH parts. Not only him saying it would be wise to wait a bit longer... but for you to say that actually, yoiu'd love to fall pregnant RIGHT AWAY. Which you didn't.
Now you're pregnant, your boyfriend has probably panicked at the thought and the rush of it (to be honest, who wouldn't?) and you both have been put in the position of having to make life-changing decisions in a short period of time. Because of a hypothetical question you asked him in the middle of passion. Very mature.
Why on earth didn't you just wait a bit longer? It looked like a promising relationship, you both were sorting out your own situations, there was really no need to start trying for a baby RIGHT NOW, was it?
Yes, posters are implying you're the most reponsible for this mess because... well... you're the person most responsible for this mess. You are the one who basically was hoping to fall pregnant 6 months after starting a new relationship, when your children don't even know the person who you wanted to be the father of your next baby. You were planning to come home one day and tell your children: hey guys, I have news... I have a new boyfriend... and by the way, I am pregnant of your new brother/sister with him! Do you really think this was a good idea? With no plans to live together, no arrangements for the baby, no discussions between you of how this was going to work?