Going from One child to Two!

What were your biggest challenges when you had your second baby? I'm nervous with how much attention my 3 year old needs, he doesn't like me to even look at other babies, he wants mommy all to himself. Has anyone experienced this, if so how did you handle it ? I'm only almost 7 weeks so there's plenty of time to get him used to the idea, just can't help but be a little nervous still