It looks like your payment and your rating of good service went to Dr. Mark, which might not be what you intended, since you're now adding significantly to the information you wanted an expert to comment on I don't know if Dr. Mark understands the effects of instant Internet communication as I do, so you might want to shift your payment, which I'm pretty sure the management will allow you to do, by simply rating me as "Excellent Service" because that will supercede "Good Service". And it looks like your boyfriend lives in Mexico?
I can look at the inconsistency issue in a different way if I factor in his business trips, his family bankruptcy, and most of all the INSTANT COMMUNICATION potential thru the Internet. The Internet and mobile internet devices make it possible to interrupt another person's activities any time day or night with a message, and then start getting worried when they don't respond in 15 minutes, or 1 hour, or 2 hours, or 3, or 4, or 6. This is HELL for interpersonal communication: Because you can't choose to be "unable to respond" without TORTURING the other person who wants you to respond RIGHT AWAY.
The most famous Existentialist drama in the 20th century was named "Huis Clos," which means No Exit (Jean Paul Sartre). In it HELL was conceived as a place like a gigantic elevator stuck between floors, so nobody could EVER leave or even get some time and space to themselves. So when a relationship went sour, there was NO ESCAPING FROM IT.
That's what Instant Messaging and Texting means to relationships! You are going crazy, as are many younger people than yourself, because you're not getting timely responses to your text messages; and he's going crazy because he can't get away from being held responsible for "standing you up" when you want him to respond to a message from you.
The answer to THIS part of the problem is simple: He needs to inform you in advance of WHEN he will make time to respond to any messages you have sent to him, like he could write: "I will be too distracted by business concerns today, but I can make some time between around 4 & 5 pm tomorrow to answer any messages from you that have come in before then." (You should probably NOT set up the expectation of actual real-time chatting at that time, because if he's stressed out about something coming up, he might not be able to keep a promise to chat. And if he has to shut down his responding because he's getting anxious about something else he needs to be thinking about or doing, then you'll get the unmistakable feeling that you're being pushed away--because your connection is being shut off--and that feels like you're not his highest priority: Because you're NOT, since he's busy with his work connections.
You would also be well advised to make some specific time predictions about when YOU will be able to respond to his messages, whether you intend to always stick to them or not. Because you need to NOT act like you're available EVERY MINUTE day and night, and here's why: The person who apparently has MORE time to devote to the relationship inherits the role of PURSUER, while the person with LESS time becomes the DISTANCER. And the distancer has more power. In addition the Pursuer starts thinking the Distancer is more SELF-centered and less interested and less loving; while the Distancer starts thinking the Pursuer is more NEEDY, childish hypersensitive, and weak. Relationships work out petter when neither partner is in one role all the time, but each one gets to experience the thoughts and feelings that are bound to occur to Pursuers and Distancers sooner or later.
So BOTH of you need to build time-sensitive EXITS into the Up- and Down- (Mood) Elevator of the Relationship you share together. Then you will not be trapped into getting hurt every time the other makes a non-response. For you are NOT engaged in Electronically Synchronized Swimming in Cyberspace halfway around the world, even though that has now become possible in "real time."