I think nobody can help you.
It's not that you are being insecure in your relationship, you don't seem to love yourself which seems to be the root of your problem. That's why you care so much if someone will be with you or you are afraid if someone will leave you. If you loved yourself enough, you would be in life enjoying your own company and enjoying sharing some things of your life with others, and an average happy person. Instead, your day is good if all is good with him, not if you feel ok inside of you. Basically your day depends on someone elses actions or decisions. Obviousy if that's the way it is, you are constantly scared if some weird message arrives to his cell phone, which is nothing you can control.
The only one that can help you is yourself, and is by starting to love yourself, start by loving small things and distinguish what is like and love, and start for yourself, that is the only way someone later will love you. Another way to look at this is to think, who will ever love someone, if that person doesn't even love himself/herself. I think it will truly help you if you stop caring of what he does, which you can if you care more about loving yourself, automatically you will start caring less of what you can't control, but you are grabbing a handle in life by things that you can control, yourself. Nobody can help you, only you can help yourself, and if it was something that truly complicates your life and you needed professional help, they can only help you if you want to be helped. But nobody can truly solve your life, because it's your life.
I used to feel like that with my boyfriend, thing is, he is so caring towards me. Anyway when got like that a friend of mine told me "if he's gonna cheat he will cheat and there is nothing you can do about it and more fool him if he did, so relax and just enjoy the relationship". It was the best bit f advice ever and now because i am more relaxed my boyfriend responds better to me now and we are happy as we always have been.
I stopped reading when you said you have not talked to him about your insecurities. There's your problem, lack of communication is going to cause a problem in a relationship. I felt insecure during my marriage and I expressed my insecurities with my husband. I told what causes it and he fixed it because he does not want me feeling insecure. You have to communicate, express your insecurities with your boyfriend and see if he will take it into consideration to help make you feel more secure in your relationship. If you do not communicate, you will become more and more bitter over time and then possibly start acting like a crazy gf. I have seen it happen, let's prevent that from happening. Talk to him.
You need some counseling. That sounds obsessive and unhealthy. Stalking him every second you aren't together is a sign of serious problems in your head. You need to work on that.