Boyfriend doesnt text back

My Boyfriend and I have a long distance relationship. Yesterday he asked me a question over text at about 4 PM and I responded right away and asked him another question and then he didn’t text me again at all the remainder of the night. I sent him another message about 10 PM to be sure he was OK and he responded just saying he was a little bit low energy all day. I am making this mean that he does not care about me because I asked him a question over text and he did not respond all day. I understand this is my thought and it’s not making me feel very good but I’m having a hard time interpreting why he would ignore me. I know I need to do some thought work on this to find a more helpful thought but I don’t know if it would be beneficial to also ask him why he didn’t respond to me all day because to me, that is a sign of disinterest. So, just thoughtwork or thoughtwork and ask him? I know he doesn’t have to follow my manual and text me back if he doesn’t want to I just want to know why.