My long distance boyfriend hasn't text me for four days, not to even say hello, is he still interested in me?

Anisui
We are in a long distance relationship for more than one year. And although we live in different continents with 6 hours time difference, we've managed to see each other every one or two months. He's come visit 3 times, me twice and have meet halfway 3 times. We don't text as much as at the beginning, but my boyfriend always texts me first everyday. Sometimes we talk a lot, sometimes only a few words just to say hello. This is basically how we communicate when he's in town. When he is abroad, on a business trip, communication is very limited. He usually goes to Asia for work and when he's there sometimes is hard to get wifi and sometimes I don't hear from him in 1 or 2 days. During this trips sometimes I'm the one who's texting first. When he travels within Europe, for 4-5 days, he usually texts me everyday or skips one day.
On Thursday he went on a business trip for 5 days, he will be back on Monday. We talked a lot and it was all ok. I expected him to text once he arrived but nothing. Then at the fourth day without hearing from him, I whatsapp him asking how he was and saying I was missing him. He replied he was ok but tired and happy to go back on Monday. We talked a little, he said it was beautiful there, then I asked for pictures of the place and he sent. In the end I asked what was one of the buildings in the picture and it seemed he was texting back but in the end I didn't get any message although I saw he was online. Later I texted again wishing him good night and a safe flight back <3. He hasn't texted back even when he's got the message and I've seen he's been online after I wrote it. Am I making a big deal out of nothing or is he being inconsiderate? I mean he's been on whatsapp, had time to do some sightseeing and take pictures but had no time to say hello, for four days? Is this a normal behavior? is ok to feel hurt and take it personally or am I just being crazy? What do you think, what should I do?
Ps.- he just text this: <3 <3 <3
My long distance boyfriend hasn't text me for four days, not to even say hello, is he still interested in me?
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