The best thing for you to do would be get out of a situation like this as quickly as possible.
The problem will only be exacerbated over time.
Possessiveness is a very serious problem and your life could end up in serious jeopardy if you do not cut the cord and move on.
Try to get support from your family and friends if you need to.
Do not lower yourself to his level, you are better that and you deserve a relationship with someone who will care about and respect you in all situations.
Too many women do not have the confidence in themselves to stand up for themselves.
If you leave this guy there will be someone else who is much better.
When you stop looking for a relationship, that is when a good one will show up.
Sometimes the people you don't even give a second look at are usually the perfect match for you.