Told my boyfriend im pregnant,should i believe he is excited ?

Hi i posted a question here yesterday about should i tell my boyfriend im pregnant i did today just to re-cap im 10 weeks pregnant have a 4 year old son he takes care of my son as if it was his own child. I didn't plan on having this baby at all and i have not dated anyone in 3 years till i met him i avoided him for 5 weeks as i was scared over the whole thing i didn't visit him i canceled him visiting me and i wouldn't answers his calls.we live 4 hours away. and im 24 hes 36.I rang him last night to come down and he did he is such a good person and committed.When i told him i was pregnant he was kinda shocked first of all? So i gave him time to think he came back and hugged me and said he is delighted and will be the best dad possible but i don't know is he that excited?4 years ago i had a boy and had to raise the child on my own which made me very weary of men i found being a single mom hard but pulled through and i think that is the reason i feel like this i am afraid he will drop out at the last minute he told me hes going to be there 100% but i would rather know if i am to raise the child now on my own or not . Does he mean what he says?and why cant i stop feeling he is going to leave me at the last minute?