It is normal to stop texting for a while, specially if you already have this relationship for a long time, as people tend to "calm down" after the first weeks.
He might be having a rough week as well, there are certain situations that might make people feel stressed, and most of the time they rather just rest from the whole ordeal rather than talking with friends/family as they normally would.
Try to talk with him (Not text) and ask him about what is going on with him these days. (Do not ask him why you haven't texted as much, you might make him feel 'pestered")
If you notice he is not interested anymore, or he simply evades conversation, it is better to move on.
Please take in mind that distance relationships are really hard to maintain, as it gives the couple a lot of freedom and time to look for "potentially better" partners.