What do you mean by "primarily in your name". Is his name on the deed or contract to purchase? Did he make payments on the house? Without knowing all these and other facts, it is impossible to answer your question. See a real estate lawyer as this situation exceeds the abilities of other realty professionals such as realtors, especially if there is no good will between you and your former boyfriend.
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Yes the short answer is he cannot sell your interest in the property without your consent and your signature. If he refuses to buy you out then you can make him sell the property through what is called in most jurisdictions a partition action. What I think you're saying by primarily is that you were the primary borrower on the loan. What matters as the other attorney mentioned is how is the property deeded. Assuming that you're both on the deed and he wants to buy you out one option is to have him assume the note and have the mortgage holder release you from the mortgage and the noteholder release you from your obligations under the note. Otherwise move to make him sell it if you want your interest in the property returned now importantly if he defaults under the note and you're still obligated under the note and your credit will be impacted as well so it sounds like it makes sense to make him sell, of course as usual seek the advice of an attorney licensed in your state.
"primarily" and "my half" are conflicting concepts. Either you own more than 50% (which is possible in a tenancy in common arrangement) or you each own "half" as joint tenants which is more typical. If you are joint tenants then you have something of an "oral partnership" to own the property and without a written agreement neither of you can theoretically sell except to each other and neither is required to do so. If, on the off-chance you do hold title as tenants in common, he could potentially sell his share to a third party. Time to see an attorney about straightening this out. You may have a strong case to "partition" the property if that makes sense, if you have been carrying 100% of the taxes, insurance, upkeep, and any loan on the property.