Why do I feel so jealous?

I’m in a relationship for 8 months now but we’ve known each other for about 5 years even though for a period of time we didn’t talk and I was on another long term relationship.

Im so jealous about everything but also the past. Everything unknown about his past bothers me. The women he’s been with in any type of way, just the thought of it haunts me. I keep asking everything and every detial about it even though I get mad about it every.single.time.

Why do I persue digging when every time I learn something it makes me sick.

Is there a serious problem going on with me? Im 25 years old.