I totally understand where you are coming from. I had a secondary (for lack of a better term) for awhile and I had this problem. It wasn't that I wanted to hear from him everyday, but at least a few times a week!
Personally, I am the kind of person that appreciates daily or at least every other day type of contact. Especially because (like you said) it only takes a moment to send a text.
Every person is different! Obviously nycindie isn't like this... so much so she doesn't even get the people that do keep in daily contact! My fiance and I have been together over four years and we text pretty much all day when we aren't together. I've never found it obsessive, claustrophobic, excessive, or overkill. I've also never felt like any of our conversations were superfluous. We don't talk to each other if we don't have anything to say and we don't talk to each other (nor take it personally) if we are busy!
Granted, all this texting will probably cease once he's back in school, right now he's just got a really boring job and I work from home so when I'm not working I text him and I take breaks at the same time as him so we can be in contact.
In any event, I agree with what most everyone else has said. You gotta talk to him. Either make a compromise or move on. But if it's something you really need/want, don't settle for less. You just gotta decide for yourself what feels right/makes you happy.
I really don't think it's true that just because you want daily contact means you are insecure. It might just be how you work! However, some of your thoughts did seem really insecure... wondering if he's found someone else, etc. So perhaps you do need to do some work yourself!
Anyway, I feel ya and I think it's best you talk to him and either get what you want, make a compromise you are both happy with, or move on. There are plenty of fish in the sea and as far as I'm concerned poly isn't about filling certain positions in your life... it's about letting relationships blossom into whatever the two of you want! This relationship might not work as him being your boyfriend... Maybe something with less pressure?