The following are things he might say, and how you SHOULD respond.
A.) “I’m thinking about you now” = I have a total hard-on and I want you to come fix it.
B.) “What are you wearing?” = Even if you have dirty sweat pants and an oversize t-shirt on tell them something really good because they are horny as hell.
C.) “What are you doing right now?” = Of course you are “Thinking about you” and wearing something similar in your answer to B above, make it REALLY good and sexy.
D.) He sends you the quintessential dick pic with a message like “I want you right now baby” = No response is necessary. Dick pics are not attractive no matter how they are taken and men should know better. That’s really just a bad decision waiting to happen. Don’t end up wearing the BDT.