Boyfriend with stutter finishes my sentences

Boyfriend with stutter finishes my sentences I’d like advice about what to do about my boyfriend who finishes my sentences. He has had a lifelong stutter that is mostly blocks of prepositional phrases. I do not have a stutter, but if I take even a slight pause when speaking he will try to finish my sentence. Or if I finish a sentence with a word he will immediately say a different synonym word. Obviously this is frustrating/irritating because I try to be patient with him even though the blocking can make his speech very lengthy and repetitive. I feel rushed even though I don’t stutter. Does anyone have experience with this?