Haven't heard from my boyfriend in 3 weeks... What should I do?

My boyfriend and I haven't seen each other for most of the summer because he had school, 3 jobs, and went overseas to visit his family for quite some time. Anyways, I eventually got a text from him at like 2 in the morning about a month ago and he was like "Guess who's back home!" And then he asked me if I wanted to get together that afternoon and I was thinking "FINALLY!!!" So I finally got to spend some time with him after two LONG months of being apart and it was just the most perfect day. He apologized for not being able to see me for so long and went on and on about how he couldn't stop thinking about me and was so worried that I might be upset with him. Before he dropped me back off at my house that night, I told him that he might not hear from me for about a week because I was going on a camping trip with my neighbors.
Shortly after I got back, I decided to shoot him a text. It just went like
Me: Hey (:
Him: Hey darling how's it going?
Me: Just chillin, missing you
Him: Aww I miss you too love.
Me: *the next morning* Sorry, I fell asleep. Wish you were there with me.
Him: Me too love
I had no idea what to reply after that, and I decided to take some time to come up with something or just hope that he texts me again later. However, I completely forgot to respond because I started school that day as well and the workload made me completely forget that I even had a phone in the first place. Two weeks went by and I still hadn't heard from him. I decided to shoot him another text that day (aka a week ago) and I got no response at all for the entire week. I was thinking of sending another text but I didn't wanna seem clingy and insane. I'm freaking out right now because despite the fact that he's always extremely busy, he has always hit me up once a week at the very least. I can't possibly think of anything I could've done to make him mad, because everything was perfectly fine between us. Should I text him again to see if everything's ok?
Haven't heard from my boyfriend in 3 weeks... What should I do?
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