What are the warning signs of a guy losing interest in you and your relationship? What things should I absolutely not wave off as "this will pass, hez just busy" or whatever..
I would say the biggest thing is lack of availability out of the blue no real change in schedule. Basically – at the beginning of the relationship – I assume he would jump through hoops to get on the phone with you, chat with you, see you, etc.
Now, it may never happen or happen very infrequently, but you may know that he is actually just as available as before, he just chooses not to spend his free time invested in you, for whatever reason. It is hard to be hurt when the person you want to feel connected with can spend time with you but opts not to. No matter what the reason is, at the end of the day, they could pick up the phone and make your day better, but they don’t, and you kind of have your answer, as shitty as it is.
If this happens, basically you have become less of a priority to them, in my experience, and it’s hard to sustain your self-respect when you are in a relationship when your dignity is in question. If you are a person who does not negotiate when your dignity is being challenged, as I am, you have no other option but to confront the situation head-on.
I suggest you state your case, and it may blow up in your face and you lose the person, but if it is actually meant to work out, things like this usually tend to strengthen a bond over the long-term and not sever ties. I think it is good if you care about the person to hold out hope as long as you can that there will be a shift; communication habits take time to correct so you may need to be patient after you confront them.
Communicating with your partner that you want more time with them should never be the impetus to break up, in my opinion. That is a normal want and it is somewhat cruel to punish somebody for wanting more of their time.