What would be the reasons for ex to keeps texting and contacting after 5 months breakup?

My on off boyfriend of 19 months packed & left in June after arguments about him cleaning up after himself, help with housework & social media. He walked out 8 times during our 19 months of relationship because of stupid reasons. Initially he wanted to keep dating & living separately but I refused. He said that he left because I kept nagging, complaining &never happy with him. He said that he feels like I don't love him for who he is (Messy person) & want to turn him into something he's not (tidy person). I said that if he just clean up after himself & help with the housework, I would not be nagging him in the first place.
He texted 11 times in July/Aug with a few sarcastic texts asking me if I enjoy my clean place, then he told me that he left some stuff at my place to which I didn't reply.
In Sept, his text changed its tone asking me if I'm OK. We texted for 4 days, planning to meet one day, which he cancelled (he said he's tired). I didn't contact him anymore. After 5 days, he asked if I would like to meet again. We texted a few days, had dinner & chat, met again for dinner & movie, texted again for 2 days, stop for 4 days, then texted again for 3 days, stop for a week, when I told him that I feel like he’s not interested, he said that he’s flat out busy with training &don’t think that we will work. I stop contact.
After 12 days, he texted me again telling me that he missed me lots & he has strong feeling but we can't live together. I replied after 10 days, texted for 3 days, met for chat, asked him if he wants me in his life, can regularly text, put us as priority, he said yes to all.
When I dropped him home, he said that he wants to focus on building his career, business & he doesn't need pressure from other area of his life. I asked for clarification, he said that he can not give me what I need.
1. what does he want from me? We didn't have sex
2. What is the reason for him to contact me?
3. What to do if he contacts me again?
4. What is going on in his head?
What would be the reasons for ex to keeps texting and contacting after 5 months breakup?
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