What is why is he leaving me on open all of a sudden?

I'm sorry to hear that you're dealing with someone leaving your messages on "open" or "read." There could be several reasons for this behavior, and while it's impossible to know for certain without more context, here are some common possibilities:

1. Busy Schedule: They might be occupied with work, school, or other commitments and aren't able to respond promptly.

2. Overwhelmed or Stressed: Life challenges could be taking up their mental space, making it difficult to engage in conversation.

3. Miscommunication or Misunderstanding: It's possible there was a misunderstanding or miscommunication that needs to be addressed.

4. Need for Space: Sometimes people need time to themselves to process their thoughts or emotions.

5. Lost Interest: Unfortunately, it might be that their level of interest has changed, and they are unsure how to communicate this directly.

6. Technical Issues: There could be a technical issue with their device or app that's preventing them from replying.

7. Waiting for a Better Time to Respond: They might be waiting until they can give your message the attention it deserves.

It's important to approach the situation with empathy and communicate openly. If you feel comfortable, consider reaching out to express how you feel and seek clarification. Keep in mind that it takes two people to maintain communication, and their level of engagement may reflect where they currently stand in the relationship.