I mentioned this earlier, but this really reminds me of the last girl I liked and seriously, even though we used to talk every day online and through texting for more than a month, she thought I was clingy after we stopped talking as frequently. And that was definitely something that changed how she looked at me.
But I had the same issue of fearing the loss of her and was basically expecting it to happen from the start, but that's really not a good way to go about things. You have to learn how to fill your time and thoughts with other things because there will be times where you won't or can't speak for a couple of days and you have to keep yourself from freaking out or thinking "he doesn't like me anymore" or stuff like that. Wait and if he doesn't respond, just keep waiting until tomorrow or the next day. You especially have to wait after that last text you sent.