Not knowing what to do

this is a really tricky situation. on the one hand, if you're not happy more often than you are happy, i'd usually say leave it. but, these are extraordinary circumstances, so maybe wait it out until you can see each other in person again and see if you feel any differently.

maybe you could see him for a walk or something?

What's important is that you communicate. Why do you feel he's been less caring/showing less affection? Has the honeymoon period ended and you're beginning to see him for who he is, or vice versa? Sometimes it's the case where feelings die down with no reason. If these are the ways that you feel, this is something you need to talk to him about.
If it's the fear of being alone that is keeping you in the relationship: it is not healthy nor sustainable for your wellbeing to keep it going.

A lot of us have been there. Imagine it like a drug withdrawal, you know it's bad for you but your brain craves the dopamine, in your instance it's him. But what's important is to understand what is rational- you may feel that being away from him for a long period of time means that you love him, which I'm very sure you do, but hold on to that moment where you had all the information needed to initiate the breakup. Time heals, but don't let nostalgia take over your rational thinking.Going to sound harsh but if your only happiness is coming from this person, maybe it's worth putting yourself in a better mental state? Partake in something you know you're good in, focus more on studies or work. Make something for yourself.