Thoughts ? / Help

I’m dealing with this guy for a few months now that I really like and things have been going really well. But lately I’ve noticed that his texting is slowing down and he’s calling a little later than usual. It hasn’t been going on long… but for like 2-3 days now. It may not seem like a big issue for some , but it is a big deal for me. I’m a person who doesn’t like sudden change. I get very anxious and start to overthink. My mind hasn’t calmed yet and I hate that I’m even made this way. I always think that someone else got their attention, they’re not interested anymore, etc. I also think that maybe they’re going through something but I always ask and they always state that they’re fine. I also ask if everything ok with us .. he claims nothing has changed on his behalf. Idk but anyways how do I stop the overthinking? How do I calm down from always feeling anxious? Are these signs that maybe he is thinking about leaving soon? Like help.