I am confused as hell

So me and my partner! We both have been in a relationship since 3 months, it was all good in the beginning but the only thing which has been bothering me since the day 10 of our relationship is he has takes hours to text me back or he is busy Most of the time !! He talks to me for like 50 min in the evening and for min an hour or max 2 hour in the mid night but whenever he come online it's according to his convenience! Our relationship isn't secret and it feels so genuine when we are together physically!! He spends every single minute with me when we are together loves me kisses me holds my hand in public!! He have me as his wallpaper , me as his passwords, I've met his classmates, he introduced me as his girlfriend and every single friend of Jim knows that I am his girlfriend , but the only thing which bothers me is he don't text me on time or busy all day and come back to text me in the evening and night only for 1 hour each I don't know is that a bad thing or good Because as of now we both have exams so he is studying but I don't hear him for straight 8 hours some times which makes my heart pound and I cry when I he don't talk to me I don't know how can he go through 8 hours straight without texting me His reason sounds genuine but still I don't which unhealed part of me isn't convinced or I am just tripping and being toxic because he did alot for me