I agree with Yoda and Kaliope.

I don't think that you should tell him now. later maybe, you will see, but not now. I don't think that you are worrying unduly, but do think that you are worrying about a wrong thing. Since you don't want repeats, you need to be worrying about avoiding repeats. In your case if seems that simply avoiding getting very drunk will preclude repeats. So the more you think through what got you in the state of being so very drunk, the easier it will be for you to develop a plan of how to not get so drunk. Of course, make sure you did not get STI's - after two weeks since the one night stand, you can already get tested for the most common STI's (if you did not use condoms, and since you were very drunk, you may not remember whether you did, so I am mentioning it). You have 4 weeks ahead of you - enough time to get reassurance that you did not pick up infections. Again, I am writing all of this because you were drunk.

You are right that alleviating your feelings of guilt at his expense is unfair to him. Plus, you are not just very early into this, but given the extreme distance, it is unclear as to how well this relationship can develop. So while being drunk can be avoided fairly easily, missing human contact, if it matters to you, is going to be a problem that will continue unless you find a way to meet frequently. Also, do realize that he might be going through something very similar as well, also worrying about what to do and whether to say anything, etc. He is as human as you are. Another option (probably the easiest for both parties) is not to promise exclusivity at this stage. Then you won't feel guilty. You can decide not to be exclusive for now, but keep daily texting and Skype, too (since you like talking more) and see what unfolds, and decide to reconsider this decision in the future if you decide to relocate, or if he decides to relocate.

Your situation is very common and stems from the fact that relationships start, develop and unfold in a myriad ways and people do not necessarily talk about what they expect from each other in terms of exclusivity so early on, especially given that your rendezvous are so "chopped up" - three days here, two there - so it is just the regular uncertainty and muddiness of daily living in the geographically separated world.