Does this guy come across as a “shy” guy or is he more on the upfront and confident side? His behavior would be dictated by his personality type.
Most guys are open books, their actions speak about their feelings. It’s best to never double guess a guy’s intentions, and just take his actions on the face value – unless he’s a “shy” type guy. If he never asked you out, it simply shows that he has a low “interest” level in you. The fact that he’s avoiding you now, and refraining from talking, is suggestive that he just wants to end it.
You say that there was a time when you were like a couple, but it’s also true that he never really asked you out during this time. So may be you felt that there was connection but he did not really feel that way. If a guy is “attracted” towards girl, he will certainly ask her out directly or indirectly. Shy guys are an exception; depending on their level of shyness they may or may not be forward enough to ask a girl out.
So unless he is a “shy” guy, the only probable reason why he did not ask you out, during the 5 months together, would be that he is not genuinely attracted to you, and he does find you to be his love interest.
In any case, the fact that he stopped talking to you all of sudden out of nowhere, does seem down right rude on his part especially since you were on “relationship” terms for 5 months. Here are a few probable reasons for this behavior on his part.
He wants to “end it” but does not want confrontation
Some guys are pretty “scared” of direct confrontations regarding break ups. In most cases they are just uncertain of the “emotional” outburst the girl might extend, and sometimes they just don’t know how to express their “disinterest” in the relationship. This could be the reason why he stopped talking to you abruptly; he did not want to continue with the farce and did not have the nerve to spell it out to you.
He’s frustrated with you
May be he tried throwing a lot of hints about his “disinterest” but you never caught on to it, and finally he was fed up with the whole thing and decided to cut it short. Look back upon your relationship and think of instances where he seemed “bored”, or distant, while in your company. How attentive was he to your conversations, and how willing was he about sharing his thoughts, and feelings, with you. Is it possible that you were living in “denial” the whole time, never wanting to come to terms with the reality that the guy did not have genuine feelings for you?
He wants “you” to approach him
This is a “small” possibility, but not a completely improbable one. May be he’s really a “shy” guy, and he wants “you” to ask him out. It’s a possibility that he was never sure of your feelings for him, and so he never asked you out. So he was just waiting for “you” to ask him out, or express your feelings to him. Since you did not do it, he got frustrated and stopped talking to you. Remember that this is a slim possibility, but if he is a shy guy this could be his “passive aggressive” way of telling you that he’s frustrated that “you” are not taking things forward.
He got to know something about you that he misunderstood
There’s a possibility that he misunderstood something you said, or may be he found out something about your past relationships, or may be someone told him something negative about you. Some guys just go into their shell instead of discussing things in the open. Since they never reveal what’s disturbing them, it’s impossible for the girl to know that there is something wrong until things go really bad. This is very true for shy guys, because they are mostly on the “sensitive” side and have a tendency to get hurt easily.
So you need decide if your boyfriend is on the “shy” side, in which case the reason why he won’t ask you out and why he’s not talking to you now, can be explained by the fact that shy guys usually expect the girl to initiate the “action”. But if he’s not the shy type, then the only reason for this behavior is that he’s not attracted to you as his love interest.