What’s the longest you’ve gone without hearing from your SO

My bf is currently at boot camp. The first couple of weeks, I’d have a letter from him almost everyday & now it’s been almost about a week and a half since I’ve heard from him. I started sending him letters the day he sent the address but idk if it ever got sent bc the day I went to the post office it was closed. I slid it in a slot that said “stamped letters.” Haven’t heard from him since and I’m getting kind of worried that maybe it’s that he doesn’t want to be with me anymore. Like he had a mindset change or something.. idk