I own a house with my ex,never married. I want the house and he’s not agreeing to let me buy him out. I just put in an ingroundpool that i paid for

You need to commence a partition action.  It is your only remedy.  While the court cannot order a buyout, it is a common settlement option.

You can't force your ex to sell his share to you, but you can force him to give you YOUR share, either by a physical partition (in the unlikely event that is practical) or by a judicial sale of the property in a partition action. Sue him for partition, and when he sees how much of his share will be spent on the fees and costs that go along with such a sale, he might agree to settle with you, since it will allow him to walk away with more money in his pocket. And next time, don't put all that money into a property that you co-own with ANYONE who isn't willing to split the costs, up front. You may or may not get them back in a partition action, but you'll probably spend a lot of money in legal fees battling it out.  And in the future, don't buy a property together with anyone (even a spouse) without a right-of-first refusal to purchase the other person's share written into the deed or in a separate agreement, in the event you can no longer live together.