Am I right to be upset or and I overreacting?

I'm worried that I'm being unreasonable. My boyfriend is moving country ( he currently lives in S.Korea and is moving to the US for work, and I live in England) and has been busy with his friends and family before he leaves. In turn, he's been a little more distant with me. he's not coming onto me anymore. he tells me he loves me every time we call( which is once every 3 days for around a hour or 2 but we text everyday) but his texts have gotten very sparse. He use to text back instantly but now he takes up to 4/5 hours if he's with friends/family. Yesterday he said he was with having dinner with his gym buddy and that he couldn't speak much and he would message me later...he didnt. so I messaged him saying hi and he replied soon after but then didn't reply after that so I thought he fell asleep(this was about 11:30pm korean time) ... He always asks me to phone him to wake him up in the morning so we can hear eachother voice before I sleep/he goes to work but I tried phoning him and it didn't go through, meaning his phone was off.. he messaged me 4 and a half hours after he usually gets up for work and said "Sorry honey,I stayed at my friends last night" ...I'm thinking the worst at this point... my ex partner of 5 years cheated on me with his recent now wife and I'm worried I'm jumping to conclusions or that I'm letting things slide too much because I think im over reacting.... please help!! :(