Should i be worried?

Been seeing this guy 5 months now, and i get so worried when he doesant text me back for ages or sometimes not at all. But when i am with him he says he wants to keep seeing me and see where this will go between us. We get on so well, he is very attentive and he says he really likes me. But i am so insecure when i dont hear back, last time i confronted him about it over email and i was convinced i was dumped for saying what i felt but he was so calm about it saying that he is just so busy with his job and family stuff, his job is very demanding and i agreed to stand by him. Is it normal to be feeling this way when he doesant write back?? Should texting back be the least of my worries when he shows it other ways? He wants to keep seeing me so why cant i just accept that whats wrong with me?? help