There is a difference from loving one and possessing one and jealousy.
It depends of there life experiences for example:
1. Experienced a traumatic death of a cherished relative,ex girlfriend so that any type of abandonment feeling comes on they feel the same experience all over again.
2. Someone in there past relationships was untrustworthy and thus they check.
3. Perhaps they think of you so much that they just want to say“How was your day ” etc
( you will see that little tidbit online on how to keep a women loving you as advise for men)?
4. They are feeling alone and “need” to have someone to be there for them. ( abandonment experience)
5. They just had an upsetting experience and needed you.( women do this too).
6. Some people have never had real love in there life so this is a new thing for them , to be valued and acknowledged etc
7.Maybe his ex cheated on him and now he is looking for it in others?
8. I would never get angry or upset with someone , but if too much then set boundaries or time limits or even call them certain times of the agreed times so that they feel a part of your life.
I had a ex boyfriend that did that and I loved that he was thinking about me that much to let me know that he cared.